Edexcel IGCSEMathematicsGeneral Applications6 Marks
Here are two functions. f(x) = 3x – 1 and g(x) = x^2 + 2
- (a)Find fg(x). Give your answer in the form ax^2 + b.[2]
- (b)Solve fg(x) = gf(x).[4]
Mark scheme
Marking points from the official mark scheme. The mark or mark type is shown in brackets.
- (a) M1 for 3(x^2 + 2) – 1
- (a) A1 for 3x^2 + 5
- (b) M1 for gf(x) = (3x – 1)^2 + 2
- (b) A1 for (3x – 1)^2 + 2 = 9x^2 – 6x + 1 + 2 = 9x^2 – 6x + 3
- (b) M1 (dep on A1 for (a) and A1 for (b)) for 3x^2 + 5 = 9x^2 – 6x + 3
- (b) A1 for x = 1/3, 1/3 oe
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