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Date May 2022 Marks available 4 Reference code 22M.1.SL.TZ1.9
Level Standard Level Paper Paper 1 Time zone Time zone 1
Command term Find Question number 9 Adapted from N/A

Question

The function f is defined by fx=2x+3x2-3, x0.

Find f'x.

[3]
a.

Find the equation of the normal to the curve y=fx at 1, 2 in the form ax+by+d=0, where a, b, d.

[4]
b.

Markscheme

f'x=-2x-2+6x  OR  f'x=-2x2+6x         A1(M1)A1


Note:
Award A1 for 6x seen, and (M1) for expressing 1x as x-1 (this can be implied from either x-2 or 2x2 seen in their final answer), A1 for -2x2. Award at most A1(M1)A0 if any additional terms are seen.

 

[3 marks]

a.

finding gradient at x=1

dydxx=1=4          A1

finding the perpendicular gradient          M1

m=-14

2=-141+c   OR   y-2=-14x-1          M1


Note: Award M1 for correctly substituting x=1 and y=2 and their m.


x+4y-9=0          A1


Note: Do not award the final A1 if the answer is not in the required form. Accept integer multiples of the equation.

 

[4 marks]

b.

Examiners report

Differentiating the function was challenging for many candidates. The most frequently obtained mark was for the term 6x. Handling the 2x term was problematic and consequently the method mark and final accuracy mark were lost.

 

a.

Some good attempts at finding the equation of the normal were seen amongst the few that answered this part. Of those that found an equation in the form ax+by+d=0 most included fractions thus hardly any fully correct answers were seen.

b.

Syllabus sections

Topic 5—Calculus » SL 5.4—Tangents and normal
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