Two functions f and g are inverse functions if and only if both of their compositions are the identity function.

That means [f o g](x) = x and [g o f](x) = x.

a)

Check to see if the compositions of f(x) and g(x) are identity functions.

Therefore, [f o g](x) and [g o f](x) are not equal, so, the functions are not inverses.

b)

Check to see if the compositions of f(x) and g(x) are identity functions.

Therefore, [f o g](x) and [g o f](x) are not equal, so, the functions are not inverses.

c)

Check to see if the compositions of f(x) and g(x) are identity functions.

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Therefore, [f o g](x) and [g o f](x) are not equal, so, the functions are not inverses.

d)

Check to see if the compositions of f(x) and g(x) are identity functions.

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Therefore, [f o g](x) and [g o f](x) equal to x, so, the functions are inverses.