Find the x-coordinates of the stationary points on the curve y = 3 lnx+x² - 7x, where x > 0.
- (a)Find the x-coordinates of the stationary points on the curve y = 3 lnx+x² - 7x, where x > 0.[5]
- (b)Determine the nature of each of these stationary points.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.
- [B2] B1 for the first term correct and one other term correct or for all terms correct with extra terms seen
- [M1] Equates their dy/dx to zero and rearranges to 3-term quadratic in x
- [M1] Dep on previous M1 Solves their 3-term quadratic
- [A1] no extra solutions x=0.5, 3 nfww isw
- [M1] FT their d²y/dx² providing B1 earned in (a)
- [A1] x=0.5, d²y/dx² <0 → max or d²y/dx² = -10 → max
- [A1] x=3, d²y/dx² >0 → min or d²y/dx² = 5/3 → min
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