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#