4MA1/2H Jun 2020, Question 12: Exponential Equations
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2H (Higher) · Calculator · 3 marks
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The question, in short
Solve 3ˣ ÷ 9³ˣ = 81 for x, showing clear algebraic working.
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Solution · 3 marks
- 19³ˣ = (3²)³ˣ = 3⁶ˣ and 81 = 3⁴
- 23ˣ ÷ 3⁶ˣ = 3ˣ⁻⁶ˣ = 3⁻⁵ˣ
- 3So 3⁻⁵ˣ = 3⁴, giving −5x = 4
- 4x = −0.8
Answer−0.8
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