Date | May 2018 | Marks available | 7 | Reference code | 18M.1.sl.TZ1.7 |
Level | SL only | Paper | 1 | Time zone | TZ1 |
Command term | Find | Question number | 7 | Adapted from | N/A |
Question
Consider f(x), g(x) and h(x), for x∈\(\mathbb{R}\) where h(x) = \(\left( {f \circ g} \right)\)(x).
Given that g(3) = 7 , g′ (3) = 4 and f ′ (7) = −5 , find the gradient of the normal to the curve of h at x = 3.
Markscheme
recognizing the need to find h′ (M1)
recognizing the need to find h′ (3) (seen anywhere) (M1)
evidence of choosing chain rule (M1)
eg \(\frac{{{\text{d}}y}}{{{\text{d}}x}} = \frac{{{\text{d}}y}}{{{\text{d}}u}} \times \frac{{{\text{d}}u}}{{{\text{d}}x}},\,\,f'\left( {g\left( 3 \right)} \right) \times g'\left( 3 \right),\,\,f'\left( g \right) \times g'\)
correct working (A1)
eg \(f'\left( 7 \right) \times 4,\,\, - 5 \times 4\)
\(h'\left( 3 \right) = - 20\) (A1)
evidence of taking their negative reciprocal for normal (M1)
eg \( - \frac{1}{{h'\left( 3 \right)}},\,\,{m_1}{m_2} = - 1\)
gradient of normal is \(\frac{1}{{20}}\) A1 N4
[7 marks]