Test Index

BECE Mathematics 2022 Paper

© africaexams.com

Question : 28

Total: 40

For what value of

x

3^x=81 ?

2
27
4
9

Solution:

Concept:

Express

81

as a power of

3

, then equate the exponents.

Explanation:

Write

81

using base

3

:

81 = 3 \times 3 \times 3 \times 3

.

By the law of indices,

a^b \times a^c = a^{b+c}

, so:

81 = 3^{1+1+1+1} = 3^4

.

Now substitute into the equation

3^x = 81

:

3^x = 3^4

.

Since the bases are equal, the exponents must be equal.

Therefore,

x = 4

.

Answer:

x = 4

, which is option C.

© africaexams.com

Go to Question:

Prev Question

Next Question