Question

Given the function f(x) = -5|x + 1| + 3, for what values of x is f(x) = -12?

Answer 1

Explanation:

This is our absolute value equation for which we want the values of x that make it true:

-5 | x + 1 | + 3 = -12. Subtracting 3 from both sides gives us

-5 | x + 1 | = = -15. Divide both sides by -5 to get

| x + 1 | = 3

This says, in words, "how many units from 3 is -1 on a number line?"

We have the following 2 equations:

x + 1 = 3 and x + 1 = -3

Solving the first one for x:

x = 2

Solving the second one for x:

x = -4

Both 2 and -4 are 3 units from -1 on a number line.

Answer 2

x = 2 or x = -4

Explanation:

-5|x + 1| + 3 = -12

Add -3 to both sides.

-5|x + 1| = -15

Divide 5 into both sides.

|x+1| = 3

Possibility 1:

x + 1=3

x = 2

Possibility 2:

x + 1 = - 3

x = -4