Question

Assume f(x)=4x+8 and g(x)=5. What is the value of (g o f)(-1)?

Answer 1

4(5)+8=28(-1)=-28 the answer is -28

Answer 2

$(g\circ f)(-1)$ is equal to $g(f(-1))$,

that is we find "g of the number f(-1)". 


Notice that we do not need to calculate f(-1) because g is the function which makes any entry equal to 5.

For example: g(500)=5, g(-750)=5 etc.; g is called a $\displaystyle{ \textit{constant function}$ because it always produces a certain constant, no matter what the input value is.

Thus, g((f(-1))=5

Answer: 5