Test Index

WAEC Mathematics 2023 Paper

© africaexams.com

Question : 40

Total: 50

Solve:

log_3 x + log_3 (x - 8) = 2

8
6
9
7

Solution:

$log_3 x + log_3 (x - 8) = 2$

$log_3 x(x - 8) = log_39$ since 2 = $log_39$

log_3

cancels out

⇒ x(x - 8) = 9

⇒

x^2 - 8x = 9

⇒

x^2 - 8x - 9 = 0

⇒

x^2 - 9x + x - 9 = 0

⇒ x(x - 9) + 1(x - 9) = 0

⇒ (x - 9)(x + 1) = 0

⇒ x = 9 or x = -1

Since we can't have a log of negative numbers,

∴ x = 9.

© africaexams.com

Go to Question:

Prev Question

Next Question