Find the equation of the tangent to the curve y = x³ + 2x² – 3x + 4 at the point where the curve crosses the y-axis.
- (i)Find the equation of the tangent to the curve y = x³ + 2x² – 3x + 4 at the point where the curve crosses the y-axis.[4]
- (ii)Find the coordinates of the point where this tangent meets the curve again.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2012). The mark or mark type is shown in brackets.
- [B1] (i) (0,4) (point where curve crosses y-axis)
- [M1] (i) for differentiation (dy/dx = 3x² + 4x – 3)
- [M1] (i) for attempt at line equation (When x = 0, dy/dx = -3)
- [A1] (i) y - 4 = -3x (or y = -3x + 4)
- [M1] (ii) for equating line and curve (-3x + 4 = x³ + 2x² – 3x + 4)
- [M1] (ii) for solution of cubic (leading to 0 = x³ + 2x²)
- [A1] (ii) x = -2
- [A1] (ii) y = 10
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