Algebra 8
3 marks · NormalGiven f(x) = 2x − 1 and g(x) = x^2. Find the value of gf(4).
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gf(4) = 49
Also accept: 49
Common mistakes: Calculating fg(4) instead of gf(4); Arithmetic errors
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Calculates f(4) = 7.
M2 · 1 mark · Substitutes f(4) = 7 into g: g(7). (follow-through)
A1 · 1 mark · States gf(4) = 7^2 = 49. (follow-through)
Worked solution
First, f(4) = 2 × 4 − 1 = 8 − 1 = 7
Then, g(7) = 7^2 = 49
So, gf(4) = 49