Answer:
This is called absolute sign | | or something near to that...
Any number inside the | | will always be positive in the output. For example |3|= 3 and also |-3|= 3
|-x| = x (notice that)
That's the bottom line and the idea of this equation
You will substitute with the value of function g(x) in the function f(g(x)) = x
The value of g(x) is known as it states g(x) = -x
So when substituting it's going to be like that
f(-x) = -x (right)?
But notice they told you that
f(x) = |x| so as we stated earlier if it's
Anything inside the | | is always positive
So f(-x) = x ###
Why?
Because when we substitute
|-x| =x