Question

What is f(-4) if f(x)=|7x-3|

Answer 1

Substitute the given into the function

f(-4) = |7(-4) - 3|
now solve
f(-4) = |-28 - 3|
f(-4) = | -31| 
the absolute value of |-31| is 31
so, 
f(-4) = 31

Hope this helps :)

Answer 2

F(-4) means subsitute -4 for every x you see in the function

f(-4)=|(7(-4)-3|
f(-4)=|-28-3|
f(-4)=|-31|

|-31| means absolute value of -31 which just takes the distance the number is from 0 (or makes it positive if it is negative and leaves it alone if it is positive)

|-31|=31
f(-4)=31