Solve the logarithmic equation Be sure to reject any value t
Solve the logarithmic equation. Be sure to reject any value that is not in the domain of the original logarithmic expressions. Give the exact answer. log_3 (x + 3) - log_3 (x - 3) = 4
Solution
Given that
log3(x + 3) - log3(x - 3) = 4
log3(x + 3) - log3(x - 3) = log3(34) [ since , a = logb(ba) ]
log3(x + 3) - log3(x - 3) = log3(81)
log3[ (x + 3)/(x - 3) ] = log3(81) [ since , logc(a) - logc(b) = logc(a/b) ]
(x + 3)/(x - 3) = 81 [ since ,if logbf(x) = logbg(x) then f(x) = g(x) ]
(x + 3) = 81(x - 3)
x + 3 = 81x - 243
81x - x = 3 + 243
80x = 246
x = 246/80
x = 123/40
x = 3.075
