Paper 1 · Exponential equations

Solve the equation $3^{x-1} + 3^{x-2} = 12$ .

x = 2

x = 3

x = 4

x = 27

Explanation:

\tfrac{3^x}{3}+\tfrac{3^x}{9}=\tfrac{4(3^x)}{9}=12

, so

3^x=27=3^3

and

x=3

Derived from ZIMSEC Mathematics Paper 1, November 2019, Q1

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