Further matrices — Question 272
Original QCE Vault practice · 5 marks
Q272 · Practice questionTechnology-activeSimple familiar5 marks
QUESTION 272 (5 marks)
Let
A=101110011,B=100010001,C=272231520. A 3×3 matrix X satisfies XA+XB=C. a)Rearrange the equation to isolate X. State the side on which the inverse must be multiplied.
[2 marks] b)Use matrix technology to determine X and verify by multiplication.
[3 marks] WORKED SOLUTION
Practice marking scheme
5 marksANSWER(a) X=C(A+B)−1; the inverse acts on the right. (b) X=031100210. Worked solution
(a) Factor on the right: X(A+B)=C. Here det(A+B)=9=0, so postmultiply by (A+B)−1. Premultiplying would not cancel the matrix adjacent to X. (b) Use the stated matrix inverse on the right. The computed matrix is
X=031100210. Multiplying this by A+B returns C entry by entry, verifying the result. Equivalent justified methods accepted; respect any requested proof method.
Exact values unless specified. Sketches assessed by mathematical features, not artistic quality.
Part a: Factor X(A+B)=C. [1 mark]Part a: Postmultiply by the correct inverse.
[1 mark]Part b: Calculate the nonsingular inverse using technology.
[1 mark]Part b: Obtain the correct X.
[1 mark]Part b: Verify X(A+B)=C. [1 mark]Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusHow many marks did you earn?Compare your working with the guide above.
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