4024/12 Oct/Nov 2021, Question 20: Matrices
Cambridge O Level Mathematics 4024 · Paper 12 (Non-calculator) · Non-calculator · 2 marks
The question, in short
Find the inverse of the 2 by 2 matrix with entries 3, −2 in the first row and 1, 2 in the second row.
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Solution · 2 marks
- 1Determinant = 3 × 2 − (−2) × 1 = 6 + 2 = 8
- 2Swap 3 and 2, change signs of −2 and 1: matrix (2 2 / −1 3)
- 3Inverse = 1/8 matrix (2 2 / −1 3)
Answer1/8 matrix (2 2 / −1 3) or matrix (1/4 1/4 / −1/8 3/8)
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