Solve 2^(x²-5x) = 1/64.
- (a)Solve 2^(x²-5x) = 1/64.[4]
- (b)By changing the base of log₂ₐ4, express (log₂ₐ4)(1 + log₂ₐ2) as a single logarithm to base a.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2014). The mark or mark type is shown in brackets.
- [M1] 2^(x^2-5x) = 2^-6 Or (x^2-5x)ln2 = ln(1/64) = -6ln2
- [M1] x²- 5x + 6 = 0 their "6"
- [M1] Correct method of solution of their 3 term quadratic
- [A1] x = 2 or x = 3
- [B1] Correct change of base to log_a 4 / log_a 2a base a only at this stage but can recover at end
- [M1] for log 2a = log 2 + log a
- [M1] log_a a = 1 used soi
- [A1] simplification to log_a 4
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