M
Math Coach Amy
Amy Ferguson Moncure

H Algebra 2/Trig · Unit 2

Solve by Factoring

Set the equation equal to zero. Factor. Set each factor equal to zero. Solve.

Jump to section:

set = 0 · factor

each factor = 0 · solve

What to Remember

1. Set equal to zero

Move every term so one side is 0. The equation is ready to factor when you see = 0.

2. Factor

Factor the quadratic completely.

3. Set each factor equal to zero

If a product is 0, at least one factor is 0. Set each factor equal to 0.

4. Solve

Solve each linear equation.

Example 1
Solve by factoring. (x + 7)(x − 3) = 0

Set both factors equal to zero and solve.

x + 7 = 0
x − 3 = 0

x = −7 and x = 3

Example 2
Solve by factoring. (x − 4)(3x + 2) = 0

Set both factors equal to zero and solve.

x − 4 = 0
3x + 2 = 0
x = 4
3x = −2
x = −23

x = 4 and x = −23

Example 3
Solve by factoring. x² + 6x + 5 = 0

x² + 6x + 5 = 0

(x + 1)(x + 5) = 0

x + 1 = 0
x + 5 = 0
x = −1
x = −5

x = −1 and x = −5

Example 4
Wait! This equation is not ready!!Set equation equal to zero.x² + 7x + 15 = 5

x² + 7x + 15 = 5

x² + 7x + 15 − 5 = 5 − 5

x² + 7x + 10 = 0

(x + 2)(x + 5) = 0

x + 2 = 0
x + 5 = 0
x = −2
x = −5

x = −2 and x = −5

Level 1

Easy

Already factored and set equal to zero.

1
Solve by factoring. (x + 5)(x − 2) = 0
Show Answer

Set both factors equal to zero and solve.

x + 5 = 0
x − 2 = 0

Answer: x = −5 and x = 2

2
Solve by factoring. (x − 6)(x + 1) = 0
Show Answer

Set both factors equal to zero and solve.

x − 6 = 0
x + 1 = 0

Answer: x = 6 and x = −1

3
Solve by factoring. (x + 4)(2x − 3) = 0
Show Answer

Set both factors equal to zero and solve.

x + 4 = 0
2x − 3 = 0
x = −4
2x = 3
x = 32

Answer: x = −4 and x = 32

4
Solve by factoring. (3x + 1)(x − 5) = 0
Show Answer

Set both factors equal to zero and solve.

3x + 1 = 0
x − 5 = 0
3x = −1
x = 5
x = −13

Answer: x = −13 and x = 5

5
Solve by factoring. (x + 8)(x + 3) = 0
Show Answer

Set both factors equal to zero and solve.

x + 8 = 0
x + 3 = 0

Answer: x = −8 and x = −3

Level 2A

Medium A

The equation is set equal to zero. Difference of squares and a = 1.

1
Solve by factoring. x² − 25 = 0
Show Answer

x² − 25 = 0

(x − 5)(x + 5) = 0

x − 5 = 0
x + 5 = 0
x = 5
x = −5

Answer: x = 5 and x = −5

2
Solve by factoring. x² + 8x + 12 = 0
Show Answer

x² + 8x + 12 = 0

(x + 6)(x + 2) = 0

x + 6 = 0
x + 2 = 0
x = −6
x = −2

Answer: x = −6 and x = −2

3
Solve by factoring. x² − 16 = 0
Show Answer

x² − 16 = 0

(x − 4)(x + 4) = 0

x − 4 = 0
x + 4 = 0
x = 4
x = −4

Answer: x = 4 and x = −4

4
Solve by factoring. x² − 3x − 10 = 0
Show Answer

x² − 3x − 10 = 0

(x − 5)(x + 2) = 0

x − 5 = 0
x + 2 = 0
x = 5
x = −2

Answer: x = 5 and x = −2

5
Solve by factoring. x² + 2x − 15 = 0
Show Answer

x² + 2x − 15 = 0

(x + 5)(x − 3) = 0

x + 5 = 0
x − 3 = 0
x = −5
x = 3

Answer: x = −5 and x = 3

Level 2B

Medium B

The equation is set equal to zero. a > 1.

1
Solve by factoring. 2x² + 5x + 2 = 0
Show Answer

2x² + 5x + 2 = 0

(2x + 1)(x + 2) = 0

2x + 1 = 0
x + 2 = 0
2x = −1
x = −2
x = −12

Answer: x = −12 and x = −2

2
Solve by factoring. 3x² + 10x + 3 = 0
Show Answer

3x² + 10x + 3 = 0

(3x + 1)(x + 3) = 0

3x + 1 = 0
x + 3 = 0
3x = −1
x = −3
x = −13

Answer: x = −13 and x = −3

3
Solve by factoring. 2x² − 7x + 3 = 0
Show Answer

2x² − 7x + 3 = 0

(2x − 1)(x − 3) = 0

2x − 1 = 0
x − 3 = 0
2x = 1
x = 3
x = 12

Answer: x = 12 and x = 3

4
Solve by factoring. 3x² − 5x − 2 = 0
Show Answer

3x² − 5x − 2 = 0

(3x + 1)(x − 2) = 0

3x + 1 = 0
x − 2 = 0
3x = −1
x = 2
x = −13

Answer: x = −13 and x = 2

5
Solve by factoring. 2x² + x − 6 = 0
Show Answer

2x² + x − 6 = 0

(2x − 3)(x + 2) = 0

2x − 3 = 0
x + 2 = 0
2x = 3
x = −2
x = 32

Answer: x = 32 and x = −2

Level 3A

Hard A

Set the equation equal to zero first. a = 1.

1
Solve by factoring. x² + 9x + 20 = 2
Show Answer

x² + 9x + 20 = 2

x² + 9x + 20 − 2 = 2 − 2

x² + 9x + 18 = 0

(x + 6)(x + 3) = 0

x + 6 = 0
x + 3 = 0
x = −6
x = −3

Answer: x = −6 and x = −3

2
Solve by factoring. x² − 2x − 8 = 7
Show Answer

x² − 2x − 8 = 7

x² − 2x − 8 − 7 = 7 − 7

x² − 2x − 15 = 0

(x − 5)(x + 3) = 0

x − 5 = 0
x + 3 = 0
x = 5
x = −3

Answer: x = 5 and x = −3

3
Solve by factoring. x² + 5x = −6
Show Answer

x² + 5x = −6

x² + 5x + 6 = −6 + 6

x² + 5x + 6 = 0

(x + 2)(x + 3) = 0

x + 2 = 0
x + 3 = 0
x = −2
x = −3

Answer: x = −2 and x = −3

4
Solve by factoring. x² + 11x + 30 = 6
Show Answer

x² + 11x + 30 = 6

x² + 11x + 30 − 6 = 6 − 6

x² + 11x + 24 = 0

(x + 8)(x + 3) = 0

x + 8 = 0
x + 3 = 0
x = −8
x = −3

Answer: x = −8 and x = −3

5
Solve by factoring. x² − 7x = −12
Show Answer

x² − 7x = −12

x² − 7x + 12 = −12 + 12

x² − 7x + 12 = 0

(x − 3)(x − 4) = 0

x − 3 = 0
x − 4 = 0
x = 3
x = 4

Answer: x = 3 and x = 4

Level 3B

Hard B

Set the equation equal to zero first. a > 1.

1
Solve by factoring. 2x² + 7x + 5 = 2
Show Answer

2x² + 7x + 5 = 2

2x² + 7x + 5 − 2 = 2 − 2

2x² + 7x + 3 = 0

(2x + 1)(x + 3) = 0

2x + 1 = 0
x + 3 = 0
2x = −1
x = −3
x = −12

Answer: x = −12 and x = −3

2
Solve by factoring. 3x² + 4x = 4
Show Answer

3x² + 4x = 4

3x² + 4x − 4 = 4 − 4

3x² + 4x − 4 = 0

(3x − 2)(x + 2) = 0

3x − 2 = 0
x + 2 = 0
3x = 2
x = −2
x = 23

Answer: x = 23 and x = −2

3
Solve by factoring. 2x² − x = 6
Show Answer

2x² − x = 6

2x² − x − 6 = 6 − 6

2x² − x − 6 = 0

(2x + 3)(x − 2) = 0

2x + 3 = 0
x − 2 = 0
2x = −3
x = 2
x = −32

Answer: x = −32 and x = 2

4
Solve by factoring. 4x² + 5x = 6
Show Answer

4x² + 5x = 6

4x² + 5x − 6 = 6 − 6

4x² + 5x − 6 = 0

(4x − 3)(x + 2) = 0

4x − 3 = 0
x + 2 = 0
4x = 3
x = −2
x = 34

Answer: x = 34 and x = −2

5
Solve by factoring. 2x² + 9x + 10 = 3
Show Answer

2x² + 9x + 10 = 3

2x² + 9x + 10 − 3 = 3 − 3

2x² + 9x + 7 = 0

(2x + 7)(x + 1) = 0

2x + 7 = 0
x + 1 = 0
2x = −7
x = −1
x = −72

Answer: x = −72 and x = −1

Mix

Mix

Six problems from Easy, Medium, and Hard.

1
Solve by factoring. x² − 5x + 6 = 0
Show Answer

x² − 5x + 6 = 0

(x − 2)(x − 3) = 0

x − 2 = 0
x − 3 = 0
x = 2
x = 3

Answer: x = 2 and x = 3

2
Solve by factoring. (x − 8)(x + 2) = 0
Show Answer

Set both factors equal to zero and solve.

x − 8 = 0
x + 2 = 0

Answer: x = 8 and x = −2

3
Solve by factoring. 3x² + 5x = 2
Show Answer

3x² + 5x = 2

3x² + 5x − 2 = 2 − 2

3x² + 5x − 2 = 0

(3x − 1)(x + 2) = 0

3x − 1 = 0
x + 2 = 0
3x = 1
x = −2
x = 13

Answer: x = 13 and x = −2

4
Solve by factoring. x² − 49 = 0
Show Answer

x² − 49 = 0

(x − 7)(x + 7) = 0

x − 7 = 0
x + 7 = 0
x = 7
x = −7

Answer: x = 7 and x = −7

5
Solve by factoring. x² + 8x + 15 = 3
Show Answer

x² + 8x + 15 = 3

x² + 8x + 15 − 3 = 3 − 3

x² + 8x + 12 = 0

(x + 6)(x + 2) = 0

x + 6 = 0
x + 2 = 0
x = −6
x = −2

Answer: x = −6 and x = −2

6
Solve by factoring. 2x² + 11x + 5 = 0
Show Answer

2x² + 11x + 5 = 0

(2x + 1)(x + 5) = 0

2x + 1 = 0
x + 5 = 0
2x = −1
x = −5
x = −12

Answer: x = −12 and x = −5

Need help solving by factoring?

Book a Session with Amy