Examples with solutions for Difference of squares: Factoring trinomials using decomposition

Exercise #1

Solve the equation:

(x−8)(x+8)+3x+17=−49 (x-8)(x+8)+3x+17=-49

Video Solution

Step-by-Step Solution

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

  • Step 1: Simplify the quadratic expression using the difference of squares formula.
  • Step 2: Combine like terms and bring all terms to one side to form a standard quadratic equation.
  • Step 3: Solve the quadratic equation using factoring or the quadratic formula.

Let's work through each step:
Step 1: The expression (x−8)(x+8)(x-8)(x+8) can be expanded using the difference of squares formula: (x−8)(x+8)=x2−64. (x-8)(x+8) = x^2 - 64.

Substituting this into the equation: x2−64+3x+17=−49. x^2 - 64 + 3x + 17 = -49.

Step 2: Combine like terms: x2+3x+17−64=−49. x^2 + 3x + 17 - 64 = -49.

Simplifying further: x2+3x−47=−49. x^2 + 3x - 47 = -49.

Add 49 to both sides to form the standard quadratic equation: x2+3x+2=0. x^2 + 3x + 2 = 0.

Step 3: Now, solve the quadratic equation. Notice that we can factor it: x2+3x+2=(x+1)(x+2)=0. x^2 + 3x + 2 = (x + 1)(x + 2) = 0.

This gives us two possible solutions: x+1=0⇒x=−1, x + 1 = 0 \quad \Rightarrow \quad x = -1, x+2=0⇒x=−2. x + 2 = 0 \quad \Rightarrow \quad x = -2.

Therefore, the solutions to the problem are x=−1,−2 x = -1, -2 .

Answer

x = -1, -2

Exercise #2

Resolve:

(x−4)(x+4)−5x=−8−x2−25x−38+4x (x-4)(x+4)-5x=-8-x^2-25x-38+4x

Video Solution

Step-by-Step Solution

To solve the given equation (x−4)(x+4)−5x=−8−x2−25x−38+4x (x-4)(x+4) - 5x = -8 - x^2 - 25x - 38 + 4x , we'll follow these steps:

Step 1: Expand the expression on the left side using the difference of squares formula:
(x−4)(x+4)=x2−16 (x-4)(x+4) = x^2 - 16 .
Substituting, we get:
x2−16−5x x^2 - 16 - 5x .

Step 2: Simplify the right-hand side expression:
Combine like terms: −x2−25x+4x−8−38 -x^2 - 25x + 4x - 8 - 38 becomes
−x2−21x−46 -x^2 - 21x - 46 .

We now have the equation:
x2−16−5x=−x2−21x−46 x^2 - 16 - 5x = -x^2 - 21x - 46 .

Step 3: Bring all terms to one side to equate to zero:
Add x2 x^2 and add 21x 21x to both sides:
x2+x2−5x+21x−16+46=0 x^2 + x^2 - 5x + 21x - 16 + 46 = 0 .
This simplifies to:
2x2+16x+30=0 2x^2 + 16x + 30 = 0 .

Step 4: Simplify further by factoring or using the quadratic formula. Factor out the common term:
x2+8x+15=0 x^2 + 8x + 15 = 0 .
This factors to:
(x+5)(x+3)=0 (x+5)(x+3) = 0 .

Setting each factor to zero gives:
x+5=0 x+5 = 0 or x+3=0 x+3 = 0 .
Thus, x=−5 x = -5 or x=−3 x = -3 .

Therefore, the solution to the equation is x=−5,−3 x = -5, -3 .

Answer

x=-5,-3

Exercise #3

Resolve:

x2−13x+3+(x−3)(x+3)=(x−6)(x+6) x^2-13x+3+(x-3)(x+3)=(x-6)(x+6)

Video Solution

Step-by-Step Solution

To solve this quadratic equation, follow these steps:

  • Step 1: Expand both sides completely.
  • Step 2: Simplify both sides to form a quadratic equation.
  • Step 3: Solve the quadratic equation using appropriate methods.

Now, let's work through the steps:

Step 1: Expand the expressions.

The left side is x2−13x+3+(x−3)(x+3) x^2 - 13x + 3 + (x-3)(x+3) . Using the difference of squares formula, expand (x−3)(x+3) (x-3)(x+3) as:

(x−3)(x+3)=x2−32=x2−9 (x-3)(x+3) = x^2 - 3^2 = x^2 - 9

Substituting back, the left side becomes:

x2−13x+3+x2−9 x^2 - 13x + 3 + x^2 - 9

The right side is (x−6)(x+6) (x-6)(x+6) . Expand using the difference of squares:

(x−6)(x+6)=x2−62=x2−36 (x-6)(x+6) = x^2 - 6^2 = x^2 - 36

Step 2: Simplify both sides.

Combine terms on the left side:

x2−13x+3+x2−9=2x2−13x−6 x^2 - 13x + 3 + x^2 - 9 = 2x^2 - 13x - 6

The right side remains:

x2−36 x^2 - 36

The equation becomes:

2x2−13x−6=x2−36 2x^2 - 13x - 6 = x^2 - 36

Subtract x2 x^2 from both sides to simplify further:

2x2−13x−6−x2=−36 2x^2 - 13x - 6 - x^2 = -36 x2−13x−6=−36 x^2 - 13x - 6 = -36

Step 3: Solve for x x .

Move -36 to the other side to form a standard quadratic equation:

x2−13x−6+36=0 x^2 - 13x - 6 + 36 = 0 x2−13x+30=0 x^2 - 13x + 30 = 0

Factor the quadratic:

(x−3)(x−10)=0 (x - 3)(x - 10) = 0

Setting each factor to zero gives:

x−3=0orx−10=0 x - 3 = 0 \quad \text{or} \quad x - 10 = 0

These lead to the solutions:

x=3andx=10 x = 3 \quad \text{and} \quad x = 10

Thus, the solutions to the equation are x=3 x = 3 and x=10 x = 10 .

Answer

10,3

Exercise #4

Solve the following equation:

5x2+7x+9=(2x−1)(2x+1) 5x^{2}+7x+9=(2x-1)(2x+1)

Video Solution

Step-by-Step Solution

Let's begin by focusing on the right side of the equation:

(2x−1)(2x+1) (2x-1)(2x+1)

We must first open the parentheses whilst multiplying all the terms as needed:

2x⋅2x+2x⋅1+−1⋅2x+−1⋅1 2x\cdot2x+2x\cdot1+-1\cdot2x+-1\cdot1

4x2+2x−2x−1 4x^2+2x-2x-1
4x2−1 4x^2-1

Let's now return to the original equation, and move all terms to the same side.

5X2+7x+9=4X2−1 5X^2+7x+9=4X^2-1
5X2−4X2+7x+9+1=0 5X^2-4X^2+7x+9+1=0
X2+7X+10=0 X^2+7X+10=0

We are left with a simple quadratic equation, which can be solved using any method we desire (factoring or the quadratic formula).

Therefore the final solution is:

X=−2,−5 X= -2,-5

Answer

2-,5-

Exercise #5

Resolve:

x2+2x−24=−13+(x−6)(x+6)+7x x^2+2x-24=-13+(x-6)(x+6)+7x

Video Solution

Step-by-Step Solution

To solve the problem, we'll start by simplifying the right side of the equation.

1. Begin by expanding the difference of squares on the right side:
(x−6)(x+6)=x2−62=x2−36(x-6)(x+6) = x^2 - 6^2 = x^2 - 36.

2. Substitute back into the equation:
x2+2x−24=−13+(x2−36)+7x x^2 + 2x - 24 = -13 + (x^2 - 36) + 7x .

3. Simplify the right side:
Combine like terms:
−13+x2−36+7x=x2+7x−49 -13 + x^2 - 36 + 7x = x^2 + 7x - 49 .

4. Now the equation is:
x2+2x−24=x2+7x−49 x^2 + 2x - 24 = x^2 + 7x - 49 .

5. Subtract x2 x^2 from both sides to eliminate x2 x^2 :
2x−24=7x−49 2x - 24 = 7x - 49 .

6. Move all terms involving x x to one side and constants to the other side:
Subtract 7x 7x from both sides:
2x−7x=−49+24 2x - 7x = -49 + 24 .
Simplify to:
−5x=−25 -5x = -25 .

7. Solve for x x by dividing both sides by −5-5:
x=−25−5=5 x = \frac{-25}{-5} = 5 .

Therefore, the solution to the problem is x=5 x = 5 .

Answer

x=5 x=5

Exercise #6

Find the value of X X :

(2x−3)(2x+3)=3x2−6x−18 (2x-3)(2x+3)=3x^2-6x-18

Video Solution

Answer

3-