A = ( (a 3) / (4 a+4) )
- (i)Find the values of the constant a for which A⁻¹ does not exist.[3]
- (ii)Given that a = 4, find A⁻¹.[2]
- (iii)Hence find the matrix B such that AB = ( (2 3) / (4 -5) ).[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [M1] For correct use of det = 0
- [M1] Dep For solution of resulting quadratic equation
- [A1] For both
- [B2] oe
- [B1] for (1/20)
- [B1] for ( (8 -3) / (-4 4) )
- [M1] For pre-multiplication by their A⁻¹
- [M1] Dep For multiplication of 2 matrices – need to see at least 2 correct elements – may be unsimplified
- [A1] For final matrix oe
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