Let f(x)=x^2+2x-15. Determine the vaules of x for which f(x)=-12?

3 Answers
Feb 7, 2018

x={-3, 1}

Explanation:

Setting f(x) = -12 gives us:

-12=x^2+2x-15

To solve quadratic equations, you need to set the equation equal to zero. By adding 12 to both sides, we get:

0=x^2+2x-3

From here, we can factor the quadratic to 0=(x+3)(x-1)

Using the Zero Product Property, we can solve the equation by setting each factor equal to zero and solving for x.

x+3=0 -> x=-3

x-1=0 -> x=1

The two solutions are -3 and 1

Feb 7, 2018

x=-3 and x=1 .

Explanation:

Put f(x)=-12

-12=x^2+2x-15
x^2+2x-15 +12=0
x^2+2x-3=0

Time to factorize now
x^2 + 3x -x -3=0
x(x+3) +(-1)(x+3)=0

take x+3 common
(x+3)(x-1)=0

x=-3 and x=1 .

Feb 7, 2018

1 or -3

Explanation:

Since f(x)=-12, then x^2+2x-15=-12. Solve this by factoring:

x^2+2x-3=0

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

x-1=0

x+3=0

The answer is

x=1,-3