Question

Given f(x)=-5x+1, solve for x when f(x)=-4.

Answer 1

f(x) = -5x+1

1. Substitute
f(x) = -5(-4) + 1

2. Expand and Simplify
-5 x -4 = 20
20+1 = 21

f(x)= 21 when f(x)= -4.

Answer 2

Answer: 1

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Step-by-step explanation:

We're told that f(x) = -4. That means we can replace the f(x) in the first equation and solve for x.

f(x) = -5x+1

-4 = -5x+1 ..... replaced f(x) with -4

-5x+1 = -4

-5x = -4-1

-5x = -5

x = -5/(-5)

x = 1

As a way to check, we plug in x = 1 to get...

f(x) = -5x+1

f(1) = -5(1)+1

f(1) = -5+1

f(1) = -4

So the answer is confirmed. If f(x) = -4, then x = 1.