How do I solve for x in 3^(2x+1) = 7^(x-2) without messy logs?
#1
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#2
I keep getting stuck when I try to solve for x in equations like 3^(2x+1) = 7^(x-2). I understand the basic log property that log(a^b) = b*log(a), but applying it here and then distributing feels messy. I end up with x terms on both sides involving logs, and my algebra gets tangled trying to isolate x.
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#3
I’ve been stuck there too. I finally took logs on both sides and treated it as a linear equation in x: (2x+1) ln3 = (x-2) ln7. It still feels clunky, but you just move the x terms to one side and isolate x.
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#4
I know the feeling. I kept ending up with x on both sides and gave up for a day. When I finally plugged it into a calculator I got x about -19.85.
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#5
I tried using base 3 logs: 2x+1 = (x-2) log_3 7, so x = (-1 - 2 log_3 7)/(2 - log_3 7). It kind of matches what the other route gives, but I’m not 100% sure about every step.
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#6
I’ve sometimes wondered if the real issue isn’t the algebra but expecting a neat number. These exponent ratios rarely land on integers.
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#7
One time I started distributing too early and tangled the terms; later I realized I should collect the x terms: x(2 ln3 - ln7) = -(ln3 + 2 ln7). Then I checked with a calculator.
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#8
If you’re unsure you’re on the right track, try a quick check by plugging in an approximate x back in and see if both sides stay close, for example around -20.
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