A-LevelMathematicsCoordinate geometry9709/12 · Oct/Nov 2015 · Q68 Marks
Points A, B and C have coordinates A (−3, 7), B (5, 1) and C (−1, k), where k is a constant.
- (i)Given that AB = BC, calculate the possible values of k.[3]
- (ii)The perpendicular bisector of AB intersects the x-axis at D. Calculate the coordinates of D.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2015). The mark or mark type is shown in brackets.
- [B1] AB = 10
- [M1] 6² + (k-1)² = 10²
- [A1] k = -7 and 9
- [B1] m of AB = -3/4
- [B1] m perp = 4/3
- [M1] M = (1, 4)
- [A1] Eqn y - 4 = (4/3)(x - 1)
- [A1] Set y to 0, → x = -2
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