Relative to an origin O, the position vectors of the points A, B, C and D are OA = (6, -3), OB = (10, 3), OC = (x, y) and OD = (12, 7)
- (a)Find the unit vector in the direction of AB.[3]
- (b)The point A is the mid-point of BC. Find the value of x and of y.[2]
- (c)The point E lies on OD such that OE : OD is 1 : 1 + λ. Find the value of λ such that BE is parallel to the x-axis.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.
- [B1] AB = (4/6)
- [M1] √(4²+6²)
- [A1] 1/√52 * (4/6) oe isw (FT provided working shown)
- [M1] (6/-3) = 1/2 * (10+x / 3+y) oe
- [A1] x = 2, y = -9
- [B1] OE = 1/(1+λ) * (12/7) oe seen
- [M1] Solves their (7/(1+λ)) = 3
- [A1] λ = 4/3 oe
- [B1] (Alternative) OE = (x_E / y_E) and identifies x_E = 12/(1+λ) and y_E = 7/(1+λ)
- [M1] (Alternative) Finds BE in terms of λ and sets y-component to zero, leading to 7/(1+λ) - 3 = 0
- [A1] (Alternative) λ = 4/3
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