The matrix A is (2 1 / 4 3).
- (i)Find (2A)⁻¹.[3]
- (ii)Hence solve the simultaneous equations 2y + 4x + 5 = 0, 6y + 8x + 9 = 0.[4]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.
- [B1] 2A=(4 2 / 8 6)
- [B2] (2A)^(-1) = 1/8 (6 -2 / -8 4); B1 for (6 -2 / -8 4) B1 for 1/8
- [B1] 4x + 2y = -5; 8x + 6y = -9
- [M1] Pre multiply (-5 / -9) by a 2x2 matrix.; Allow recovery
- [M1] (x / y) = 1/8 (6 -2 / -8 4) (-5 / -9); Pre multiply their (-5 / -9) by their answer to (i)
- [A2] (x / y) = 1/8 (-12 / 4) (= -1.5 / 0.5); A1 for x value A1 for y value oe Allow both unsimplified
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