Question

A function follows the rule y = -75 - 5x. When the function's output is 25, the equation is 25 = -75 - 5x. What is the function input when the output is 25?

Answer 1

The function input is -20 when the output is 25

Explanation:

we have

`y=-75-5x`

where

y is the dependent variable or output

x is the independent variable or input

If the output is 25

then

y=25

substitute

`25=-75-5x`

Solve for the function input is the same that solve for x

Isolate the variable x

Adds 5x both sides

`25+5x=-75-5x+5x`

`25+5x=-75`

subtract 25 both sides

`25+5x-25=-75-25`

`5x=-100`

Divide by 5 both sides

`x=-20`

therefore

The function input is -20 when the output is 25