Short Multiplication Formulas - Examples, Exercises and Solutions

Question Types:
Difference of squares: Complete the missing numbersDifference of squares: Equations with denominatorsDifference of squares: Finding the Domain of a Square Root FunctionDifference of squares: Identify the greater valueDifference of squares: More than one factorizationDifference of squares: Number of termsDifference of squares: Using fractionsDifference of squares: Using multiple rulesDifference of squares: Using quadrilateralsDifference of squares: Using rootsDifference of squares: Worded problemsSquare of Difference: Complete the missing numbersSquare of Difference: Data with powers and rootsSquare of Difference: Equations with denominatorsSquare of Difference: Equations with variables on both sidesSquare of Difference: Identify the greater valueSquare of Difference: More than one factorizationSquare of Difference: Number of termsSquare of Difference: Resulting in a quadratic equationSquare of Difference: Solving the problemSquare of Difference: System of equations with no solutionSquare of Difference: Transition between expressionsSquare of Difference: Using fractionsSquare of Difference: Using multiple rulesSquare of Difference: Using quadrilateralsSquare of sum: Complete the missing numbersSquare of sum: Data with powers and rootsSquare of sum: Domain of definitionSquare of sum: Equations with denominatorsSquare of sum: Equations with variables on both sidesSquare of sum: Equations with Variables on One SideSquare of sum: Identify the greater valueSquare of sum: More than one factorizationSquare of sum: Number of termsSquare of sum: Resulting in a quadratic equationSquare of sum: Solving the problemSquare of sum: System of equations with no solutionSquare of sum: Transition between expressionsSquare of sum: Using fractionsSquare of sum: Using multiple rulesSquare of sum: Using quadrilateralsSquare of sum: Using short multiplication formulasSquare of sum: Using variables

What are Abbreviated Multiplication Formulas?

Abbreviated multiplication formulas, also known as algebraic identities, are shortcuts that simplify the process of expanding and factoring expressions. These formulas save time and reduce the steps required for complex calculations. Abbreviated multiplication formulas will be used throughout our math studies, from elementary school to high school. In many cases, we will need to know how to expand or add these equations to arrive at the solution to various math exercises.

Abbreviated Multiplication Formulas for 2nd degree

Here are the basic formulas for abbreviated multiplication:

The square of the sum:
(X+Y)2=X2+2XY+Y2(X + Y)^2=X^2+ 2XY + Y^2

The squared difference:

(XY)2=X22XY+Y2(X - Y)^2=X^2 - 2XY + Y^2

The difference of squares:

(X+Y)×(XY)=X2Y2(X + Y)\times (X - Y) = X^2 - Y^2

Visual breakdown of abbreviated multiplication formulas: (a+b)² = a² + 2ab + b² and (a−b)² = a² − 2ab + b², with color-coded area models representing the expansion of binomials


Abbreviated Multiplication Formulas for 3rd degree

Abbreviated multiplication formulas for 3rd-degree expressions, also known as cubic identities, build upon the concepts of the 2nd-degree formulas we’ve already covered. The key difference is the adjustment for working with cubic (3rd-degree) terms instead of quadratic (2nd-degree) terms. These formulas simplify complex cubic expressions, breaking them into manageable parts to make calculations faster and more efficient. They are particularly useful in solving problems involving volumes of cubes and other 3D shapes or in advanced mathematics, such as polynomial factoring and equation solving.

Here are two of the most common abbreviated multiplication formulas for 3rd-degree expressions:

Cube of a Sum

(a+b)3=a3+3a2b+3ab2+b3(a+b)^3=a^3+3a^2 b+3ab^2+b^3

Cube of a Difference

​​​​​​​(ab)3=a33a2b+3ab2b3​​​​​​​(a-b)^3=a^3-3a^2 b+3ab^2-b^3


Abbreviated Multiplication Formulas Verification and Examples

We will test the shortcut multiplication formulas by expanding the parentheses.

Square of a Sum:

(X+Y)2=(X+Y)×(X+Y)=(X + Y)^2 = (X + Y)\times (X+Y) =

X2+XY+YX+Y2=X^2 + XY + YX + Y^2=

Since: XY=YXXY = YX

X2+2XY+Y2X^2 + 2XY + Y^2

Example:

(x+3)2 (x+3)^2

(x+3)2=x2+2(x)(3)+32=x2+6x+9 (x+3)^2=x^2+2(x)(3)+3^2=x^2+6x+9


Square of a Difference:

(XY)2=(XY)×(XY)=(X - Y)^2 = (X - Y)\times (X-Y) =

X2XYYX+Y2=X^2 - XY - YX + Y^2=

Since:XY=YX XY = YX

X22XY+Y2X^2 - 2XY + Y^2

Example:

(x4)2 (x−4)^2

(x4)2=x22(x)(4)+42=x28x+16 (x−4)^2=x^2−2(x)(4)+4^2=x^2−8x+16


Product of a Sum and a Difference:

(X+Y)×(XY)=(X + Y)\times (X-Y) =

X2XY+YXY2=X^2 - XY + YX - Y^2=

Since: XY=YX XY = YX

XY+YX=0 - XY + YX = 0

X2Y2X^2 - Y^2

Example:

(x+5)(x5) (x+5)(x−5)

(x+5)(x5)=x252=x225 (x+5)(x−5)=x^2−5^2=x^2−25


Using Abbreviated Multiplication Formulas to Shift the Expression Both Ways

It’s important to remember that these formulas are not one-sided; you can use them to switch between different forms of an expression as needed. For example, you can use the formula:

(X+Y)2=X2+2XY+Y2(X + Y)^2=X^2+ 2XY + Y^2

to expand an expression in parentheses into its expanded form. Conversely, if you encounter an expression like

X2+2XY+Y2X^2+ 2XY + Y^2

you can factor it back into

(X+Y)2(X + Y)^2

This flexibility allows you to work with the representation that is most useful for the problem at hand, whether it’s simplifying, solving, or analyzing the expression. Understanding this two-way functionality is essential for mastering algebraic manipulation.

Practice Short Multiplication Formulas

Examples with solutions for Short Multiplication Formulas

Exercise #1

Choose the expression that has the same value as the following:

(x+y)2 (x+y)^2

Video Solution

Step-by-Step Solution

To solve this problem, we will use the formula for the square of a sum, which is (a+b)2=a2+2ab+b2(a+b)^2 = a^2 + 2ab + b^2.

Here, we identify a=x a = x and b=y b = y . Thus, our expression (x+y)2 (x+y)^2 can be expanded as follows:

(x+y)2=x2+2xy+y2 (x+y)^2 = x^2 + 2xy + y^2

Now we will match this expanded form with the given choices.

  • Choice 1: x2+y2 x^2 + y^2 - This is missing the middle term 2xy 2xy .
  • Choice 2: y2+x2+2xy y^2 + x^2 + 2xy - This matches the expanded expression.
  • Choice 3: x2+xy+y2 x^2 + xy + y^2 - The term xy xy doesn't match the required 2xy 2xy .
  • Choice 4: x22xy+y2 x^2 - 2xy + y^2 - The middle term has an incorrect sign.

Therefore, the expression that is equivalent to (x+y)2 (x+y)^2 is choice 2: y2+x2+2xy y^2 + x^2 + 2xy .

Answer

y2+x2+2xy y^2+x^2+2xy

Exercise #2

Choose the expression that has the same value as the following:


(x+3)2 (x+3)^2

Video Solution

Step-by-Step Solution

We use the abbreviated multiplication formula:

x2+2×x×3+32= x^2+2\times x\times3+3^2=

x2+6x+9 x^2+6x+9

Answer

x2+6x+9 x^2+6x+9

Exercise #3

Choose the expression that has the same value as the following:

(xy)2 (x-y)^2

Video Solution

Step-by-Step Solution

We use the abbreviated multiplication formula:

(xy)(xy)= (x-y)(x-y)=

x2xyyx+y2= x^2-xy-yx+y^2=

x22xy+y2 x^2-2xy+y^2

Answer

x22xy+y2 x^2-2xy+y^2

Exercise #4

Choose the expression that has the same value as the following:

(x7)2 (x-7)^2

Video Solution

Step-by-Step Solution

To solve the problem, we need to expand the expression (x7)2(x-7)^2 using the formula for the square of a difference.

The formula for the square of a difference is (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2.

Let's apply this formula to our expression (x7)2(x-7)^2:

  • Identify a=xa = x and b=7b = 7.
  • Substitute these values into the formula: (x7)2=x22(x)(7)+72(x-7)^2 = x^2 - 2(x)(7) + 7^2.
  • Calculate each term:
    • x2x^2 remains as x2x^2.
    • 2(x)(7)=14x-2(x)(7) = -14x.
    • 72=497^2 = 49.

So, expanding the expression, we get x214x+49x^2 - 14x + 49.

Thus, the expression that has the same value as (x7)2(x-7)^2 is x214x+49x^2 - 14x + 49.

Answer

x214x+49 x^2-14x+49

Exercise #5

(x26)2= (x^2-6)^2=

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify a and b in the expression (x26)2 (x^2 - 6)^2 .
  • Step 2: Apply the square of a difference formula.
  • Step 3: Simplify the resulting expression.

Now, let's work through each step:
Step 1: The expression is (x26)2 (x^2 - 6)^2 . Here, a=x2 a = x^2 and b=6 b = 6 .
Step 2: Apply the binomial formula: (ab)2=a22ab+b2 (a - b)^2 = a^2 - 2ab + b^2 .
Step 3:
1. Calculate a2 a^2 :
a2=(x2)2=x4 a^2 = (x^2)^2 = x^4 .
2. Calculate 2ab 2ab :
2ab=2(x2)(6)=12x2 2ab = 2(x^2)(6) = 12x^2 .
3. Calculate b2 b^2 :
b2=62=36 b^2 = 6^2 = 36 .
4. Substitute these back into the formula:
(x26)2=x412x2+36(x^2 - 6)^2 = x^4 - 12x^2 + 36.

Therefore, the expanded expression is x412x2+36 x^4 - 12x^2 + 36 .

Answer

x412x2+36 x^4-12x^2+36

Exercise #6

(xx2)2= (x-x^2)^2=

Video Solution

Step-by-Step Solution

To solve the expression (xx2)2(x-x^2)^2, we will use the square of a binomial formula (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2.

Let's identify aa and bb in our expression:

  • Here, a=xa = x and b=x2b = x^2.

Applying the formula:

(xx2)2=(x)22(x)(x2)+(x2)2(x - x^2)^2 = (x)^2 - 2(x)(x^2) + (x^2)^2

Calculating each part, we get:

  • (x)2=x2(x)^2 = x^2
  • 2(x)(x2)=2x3-2(x)(x^2) = -2x^3
  • (x2)2=x4(x^2)^2 = x^4

Combining these results, the expression simplifies to:

x42x3+x2x^4 - 2x^3 + x^2

Therefore, the expanded form of (xx2)2(x-x^2)^2 is x42x3+x2\boxed{x^4 - 2x^3 + x^2}.

Answer

x42x3+x2 x^4-2x^3+x^2

Exercise #7

Solve:

(2+x)(2x)=0 (2+x)(2-x)=0

Video Solution

Step-by-Step Solution

We use the abbreviated multiplication formula:

4x2=0 4-x^2=0

We isolate the terms and extract the root:

4=x2 4=x^2

x=4 x=\sqrt{4}

x=±2 x=\pm2

Answer

±2

Exercise #8

(4b3)(4b3) (4b-3)(4b-3)

Rewrite the above expression as an exponential summation expression:

Video Solution

Step-by-Step Solution

To solve this problem, we will apply the square of a binomial formula.

The given expression is (4b3)(4b3)(4b-3)(4b-3). We recognize this as the square of a binomial, which can be rewritten as (4b3)2(4b-3)^2. To expand this expression, we use the formula:

(ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2

In our expression, a=4ba = 4b and b=3b = 3. Let's apply the formula:

  • Calculate a2a^2:
    a2=(4b)2=16b2a^2 = (4b)^2 = 16b^2
  • Calculate 2ab-2ab:
    2ab=2(4b)(3)=24b-2ab = -2(4b)(3) = -24b
  • Calculate b2b^2:
    b2=(3)2=9b^2 = (3)^2 = 9

Putting it all together, we have:

(4b3)2=16b224b+9(4b-3)^2 = 16b^2 - 24b + 9

Therefore, the exponential summation expression is (4b3)2(4b-3)^2, with the expanded form:

16b224b+916b^2 - 24b + 9

This matches choice 3, confirming our solution.

Answer

(4b3)2 (4b-3)^2

16b224b+9 16b^2-24b+9

Exercise #9

Rewrite the following expression as an addition and as a multiplication:

(3xy)2 (3x-y)^2

Video Solution

Step-by-Step Solution

To solve this problem, let's start by identifying the parts of the binomial:

  • The expression (3xy)2(3x-y)^2 represents a binomial squared.
  • We recognize it has the form (ab)2(a-b)^2 where a=3xa = 3x and b=yb = y.
  • Using the formula for the square of a difference: (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2, we find the expanded form.

Let's apply the formula:

Step 1: Expand (3xy)2(3x-y)^2 using the formula:
(3xy)2=(3x)22(3x)(y)+y2(3x-y)^2 = (3x)^2 - 2(3x)(y) + y^2

Step 2: Calculate each part:
(3x)2=9x2(3x)^2 = 9x^2
2(3x)(y)=6xy-2(3x)(y) = -6xy
y2y^2 stays as y2y^2

Step 3: Combine these results to get the addition form:
9x26xy+y29x^2 - 6xy + y^2

The expression in multiplication form, as provided, is just repeating the factors:
(3xy)(3xy)(3x-y)(3x-y)

Therefore, the expression rewritten as addition is 9x26xy+y29x^2 - 6xy + y^2 and as multiplication (3xy)(3xy)(3x-y)(3x-y).

Answer

9x26xy+y2 9x^2-6xy+y^2

(3xy)(3xy) (3x-y)(3x-y)

Exercise #10

(a4)(a4)=? (a-4)(a-4)=\text{?}

Video Solution

Step-by-Step Solution

To solve the problem, we will expand the expression (a4)(a4)(a-4)(a-4) using the square of a difference formula.

This formula states: (xy)2=x22xy+y2(x-y)^2 = x^2 - 2xy + y^2.
In our case, x=ax = a and y=4y = 4, so we apply the formula:

  • First term: x2=a2x^2 = a^2
  • Second term: 2xy=2a4=8a-2xy = -2 \cdot a \cdot 4 = -8a
  • Third term: y2=42=16y^2 = 4^2 = 16

Putting it all together, the expression becomes:
a28a+16a^2 - 8a + 16.

After matching this result with the given choices, we find it corresponds to choice 4.

Therefore, the solution to the problem is a28a+16\mathbf{a^2 - 8a + 16}.

Answer

a28a+16 a^2-8a+16

Exercise #11

Declares the given expression as a sum

(7b3x)2 (7b-3x)^2

Video Solution

Step-by-Step Solution

To solve for (7b3x)2(7b - 3x)^2 as a sum, we'll follow these steps:

  • Step 1: Identify the given expression and apply the formula for the square of a difference:
    (ab)2=a22ab+b2(a - b)^2 = a^2 - 2ab + b^2 where a=7ba = 7b and b=3xb = 3x.
  • Step 2: Expand each term:
    • a2=(7b)2=49b2a^2 = (7b)^2 = 49b^2
    • 2ab=2×7b×3x=42bx-2ab = -2 \times 7b \times 3x = -42bx
    • b2=(3x)2=9x2b^2 = (3x)^2 = 9x^2
  • Step 3: Combine all terms to form the sum:
    (7b3x)2=49b242bx+9x2 (7b - 3x)^2 = 49b^2 - 42bx + 9x^2 .

Therefore, the solution to the problem is (7b3x)2=49b242bx+9x2(7b - 3x)^2 = 49b^2 - 42bx + 9x^2.

Hence, the correct answer choice is: 49b242bx+9x2 49b^2 - 42bx + 9x^2

Answer

49b242bx+9x2 49b^2-42bx+9x^2

Exercise #12

4x2+20x+25= 4x^2+20x+25=

Video Solution

Step-by-Step Solution

In this task, we are asked to simplify the formula using the abbreviated multiplication formulas.

Let's take a look at the formulas:

(xy)2=x22xy+y2 (x-y)^2=x^2-2xy+y^2

 (x+y)2=x2+2xy+y2 (x+y)^2=x^2+2xy+y^2

(x+y)×(xy)=x2y2 (x+y)\times(x-y)=x^2-y^2

Taking into account that in the given exercise there is only addition operation, the appropriate formula is the second one:

Now let us consider, what number when multiplied by itself will equal 4 and what number when multiplied by itself will equal 25?

The answers are respectively 2 and 5:

We insert these into the formula:

(2x+5)2= (2x+5)^2=

(2x+5)(2x+5)= (2x+5)(2x+5)=

2x×2x+2x×5+2x×5+5×5= 2x\times2x+2x\times5+2x\times5+5\times5=

4x2+20x+25 4x^2+20x+25

That means our solution is correct.

Answer

(2x+5)2 (2x+5)^2

Exercise #13

(x2+4)2= (x^2+4)^2=

Video Solution

Step-by-Step Solution

To solve the expression (x2+4)2 (x^2 + 4)^2 , we will follow these steps:

  • Step 1: Identify the expression as a binomial (a+b) (a + b) , where a=x2 a = x^2 and b=4 b = 4 .
  • Step 2: Apply the binomial square formula: (a+b)2=a2+2ab+b2 (a + b)^2 = a^2 + 2ab + b^2 .
  • Step 3: Substitute a a and b b into the formula.
  • Step 4: Calculate each term in the formula.
  • Step 5: Simplify to arrive at the final expanded form.

Let's execute these steps:
Step 1: Identify a=x2 a = x^2 and b=4 b = 4 .
Step 2: Apply the formula (a+b)2=a2+2ab+b2 (a + b)^2 = a^2 + 2ab + b^2 .
Step 3: Substitute to get: (x2)2+2(x2)(4)+42 (x^2)^2 + 2(x^2)(4) + 4^2 .
Step 4: Calculate each term:
- (x2)2=x4 (x^2)^2 = x^4 ,
- 2(x2)(4)=8x2 2(x^2)(4) = 8x^2 ,
- 42=16 4^2 = 16 .
Step 5: Combine the terms to get the expanded expression: x4+8x2+16 x^4 + 8x^2 + 16 .

Therefore, the solution to the expression is x4+8x2+16 x^4 + 8x^2 + 16 .

Answer

x4+8x2+16 x^4+8x^2+16

Exercise #14

(x+x2)2= (x+x^2)^2=

Video Solution

Step-by-Step Solution

To solve this problem, follow these steps:

  • Step 1: Identify the terms: Here, a=x a = x and b=x2 b = x^2 .
  • Step 2: Apply the square of a binomial formula: (a+b)2=a2+2ab+b2(a + b)^2 = a^2 + 2ab + b^2.
  • Step 3: Substitute the terms into the formula and simplify the resulting expression.

Now, let's work through each step:

Step 1: We have a=xa = x and b=x2b = x^2.
Step 2: The formula gives us: (a+b)2=a2+2ab+b2 (a + b)^2 = a^2 + 2ab + b^2

Step 3: Substituting a=xa = x and b=x2b = x^2 into the formula:

(x+x2)2=(x)2+2(x)(x2)+(x2)2 (x + x^2)^2 = (x)^2 + 2(x)(x^2) + (x^2)^2

This simplifies to:

x2+2x3+x4 x^2 + 2x^3 + x^4

Therefore, the expanded form of the expression (x+x2)2 (x + x^2)^2 is x2+2x3+x4\mathbf{x^2 + 2x^3 + x^4}.

This matches with choice 3 from the options provided.

Answer

x2+2x3+x4 x^2+2x^3+x^4

Exercise #15

9x212x+4= 9x^2-12x+4=

Video Solution

Step-by-Step Solution

To rewrite the expression 9x212x+4 9x^2 - 12x + 4 as a perfect square, follow these steps:

  • Step 1: Compare the expression 9x212x+4 9x^2 - 12x + 4 with (ab)2(a - b)^2.
  • Step 2: Note that (ab)2=a22ab+b2(a - b)^2 = a^2 - 2ab + b^2.
  • Step 3: Identify matching terms: a2=9x2a^2 = 9x^2, 2ab=12x-2ab = -12x, b2=4b^2 = 4.

Now, separate this into steps:
Step 1: Set a2=9x2a^2 = 9x^2, so a=3xa = 3x.
Step 2: Set b2=4b^2 = 4, so b=2b = 2.
Step 3: Verify 2ab=12x-2ab = -12x:
2×3x×2=12x.-2 \times 3x \times 2 = -12x.
This confirms our values of aa and bb are correct.

Thus, the expression 9x212x+4 9x^2 - 12x + 4 is equivalent to the square (3x2)2(3x - 2)^2.

The correct choice is: (3x2)2 (3x-2)^2 .

Answer

(3x2)2 (3x-2)^2