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Date May Example question Marks available 2 Reference code EXM.1.AHL.TZ0.45
Level Additional Higher Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number 45 Adapted from N/A

Question

Let A = (123212332)123212332D = (4137274395)4137274395, and C = (5710)5710

Given matrices A, B, C for which AB = C and det A ≠ 0, express B in terms of A and C.

[2]
a.

Find the matrix DA.

[1]
b.i.

Find B if AB = C.

[2]
b.ii.

Find the coordinates of the point of intersection of the planes x+2y+3z=5x+2y+3z=52xy+2z=72xy+2z=73x3y+2z=103x3y+2z=10.

[2]
c.

Markscheme

Since det A ≠ 0, A–1 exists.     (M1)

Hence AB = C ⇒ B = A–1C          (C1)

[2 marks]

a.

DA(100010001)100010001          (A1)

[1 mark]

b.i.

B = A–1C = DC         (M1)

=(112)=112         (A1)

[2 marks]

b.ii.

The system of equations is x+2y+3z=52xy+2z=73x3y+2z=10x+2y+3z=52xy+2z=73x3y+2z=10

or A(xyz)=xyz= C         (M1)

The required point = (1, –1, 2).         (A1)

[2 marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.i.
[N/A]
b.ii.
[N/A]
c.

Syllabus sections

Topic 1—Number and algebra » AHL 1.14—Introduction to matrices
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Topic 1—Number and algebra

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