Question

3 log (x^2 + 1) . 5 log 3 = 5 log (x+21) apabila x = ...
A. 3
B. 4
C. 5
D. -5 atau 4
E. -4 atau 5

Note
= letak 3 diatas log (x^2 +1)
= letak 5 diatas log 3
= letak 5 diatas log (x+21)

Answer 1

Verified answer

LogAritMa

5'log 3 . 3'log (x² + 1) = 5'log (x + 21)
5'log (x² + 1) = 5'log (x + 21)
x² + 1 = x + 21
x² - x + 1 - 21 = 0
(x - 5)(x + 4) = 0
x = 5 atau x = -4

Opsi : E