Answer: Choice D) x
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Step-by-step explanation:
The composition of the original function with its inverse will cancel out the operations to yield the input as the output.
Consider the example functions shown below
The first function adds 5 while the second function does the complete opposite and subtract 5. The two functions are inverses of each other.
We see that,
f(x) = x+5
f(g(x)) = g(x)+5
f(g(x)) = x-5+5
f(g(x)) = x
and you should find that g(f(x)) = x for similar steps.
No matter what the x input is, the output will be identical to the input.
For instance, if we plug in x = 7, then adding 5 to it gets us 12. Then undoing that operation to subtract 5 gets us back to 7 again. This is one example showing why both f(g(x)) and g(f(x)) both equal x, where f and g are inverses of each other.