Algebra 8

4 marks · Hard

A function is defined by .

Let the function be defined by .

Calculate the value of the composite function . Show your working.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

Also accept: 41; fg(-3) = 41

Common mistakes: Calculating gf(-3) instead of fg(-3); Not following correct order of operations

Show mark scheme and worked solution

Marking points

M1 · 1 mark · Find g(-3) correctly: substitute -3 into g(x).

M2 · 1 mark · Substitute the result from g(-3) into f(x) correctly. (follow-through)

A1 · 1 mark · Correct evaluation of g(-3) = 18.

A2 · 1 mark · Correct final answer: . (follow-through)

Worked solution

First, evaluate :

Now, use this result in the function f:

(Correction: The correct final answer is 86.)