A curve has equation y = 7 + 4 ln(2x + 5). Find the equation of the tangent to the curve at the point (−2, 7), giving your answer in the form y = mx + c.
- (a)A curve has equation y = 7 + 4 ln(2x + 5). Find the equation of the tangent to the curve at the point (−2, 7), giving your answer in the form y = mx + c.[5]
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2022). The mark or mark type is shown in brackets.
- [M1] Differentiate to obtain form k/(2x+5) [Any non-zero constant k]
- [A1] Obtain correct 8/(2x+5)
- [A1] Substitute x = -2 to obtain gradient 8
- [M1] Attempt equation of tangent through (-2, 7) with numerical gradient
- [A1] Obtain y = 8x + 23
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