The formula for the difference of squares

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Difference of Squares Formula

The difference of squares formula is another key algebraic shortcut that simplifies expressions involving two squared terms subtracted from each other. It is written as:

(XY)2=X22XY+Y2(X - Y)^2=X^2 - 2XY + Y^2
This formula skips the need for full expansion and directly factors the expression. It works for both numerical and algebraic expressions, making it versatile in solving equations and simplifying terms. That is, when we encounter two numbers with a minus sign between them, that is, the difference and they will be in parentheses and raised as a squared expression, we can use this formula.

For (xy)2(x - y)^2 the full expansion would be:
(xy)2=(xy)(xy)=xx+x(y)yxy(y)=x22xy+y2(x - y)^2=(x-y)(x−y)=x⋅x+x⋅(-y)-y⋅x−y⋅(-y)=x^2-2xy+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

Example:

(a4)2=(a - 4)^2=
a×a+a×(4)+(4)×a+(4)×(4)=a\times a+a\times (-4)+ (-4)\times a + (-4) \times (-4) =
a2+2(4a)+(4)2=a^2+2(-4a)+ (-4)^2 =
a28a+16a^2-8a+16

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Test yourself on square of difference!

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

\( (x-y)^2 \)

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Pay attention - The formula also works in non-algebraic expressions or combinations with numbers and unknowns.

Let's look at an example

(X7)2=(X-7)^2=
Here we identify two elements between which there is a minus sign and they are enclosed in parentheses and raised to the square as a single expression.
Therefore, we can use the formula for the difference of squares.
We will work according to the formula and pay attention to the minus and plus signs.
We will obtain: 
(X7)2=x214x+49(X-7)^2=x^2-14x+49
Indeed, we pronounce the same expression differently using the formula.


If you are interested in this article, you might also be interested in the following articles:

Square

The area of a square

Multiplication of the sum of two elements by the difference between them

The formula for the sum of squares

The formulas that refer to two expressions to the power of 3

In the blog of Tutorela you will find a variety of articles about mathematics.


Examples and exercises with solutions of the difference of squares formula

Exercise #1

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 #2

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 #3

(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 #4

(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 #5

(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

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