ECZ 2019 · O-Level Paper 2 · Question 6 — Vectors In Two Dimensions

In the diagram, OB = 4OA and AC = 5AX. M is the midpoint of BC, OA = a and BM = b.

(a(i)(a)) In the diagram, OB = 4OA and AC = 5AX, M is the midpoint of BC, OA = a and BM = b. Express AB in terms of a andorb.[1]

Diagram for part (a(i)(a))

Verified working — step 1

OB = 4OA = …

(a(i)(b)) Express AC in terms of a andorb.[1]

Diagram for part (a(i)(b))

Verified working — step 1

M is the midpoint of BC, so BC = 2BM = …

(a(i)(c)) Express OM in terms of a andorb.[1]

Diagram for part (a(i)(c))

Verified working — step 1

OM = OB + BM = …

(a(ii)) Show that OX = (25)(4a + b).[2]

Diagram for part (a(ii))

Verified working — step 1

Since AC = 5AX, AX = (15)AC = (15)(3a + 2b).

(b) Find the equation of the normal to the curve y = 5x3 - 6x2 + 2x + 5 at the point (1, 2).[3]

Verified working — step 1

dydx= 15x2 - 12x + 2

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Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.

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