Show that the equation log₃(2x + 1) = 1 + 2log₃(x – 1) can be written as a quadratic equation in x.
- (a)Show that the equation log₃(2x + 1) = 1 + 2log₃(x – 1) can be written as a quadratic equation in x.[3]
- (b)Hence solve the equation log₃ (4y + 1) = 1 + 2 log₃(2y – 1), giving your answer correct to 2 decimal places.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.
- [M1] Use law of logarithm of a power
- [B1] Use log₃3 = 1
- [A1] Obtain 3x²−8x+2=0 or 1.5x² − 4x+1=0
- [M1] Solve 3-term quadratic equation from part 3(a) or restart to find y
- [A1] Obtain answer 1.19
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