Solving for x: log4 (x - 10) + log4 (x + 10) = 4
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Originally Posted by tmac11522 Solving for x: log4 (x - 10) + log4 (x + 10) = 4 $\displaystyle log_a(m) + log_a(n) = log_a{(mn)}$ in your case $\displaystyle log_4{((x+10)(x-10))} = 4$ $\displaystyle log_4{(x^2-100)} = 4$ $\displaystyle x^2-100=4^4$ $\displaystyle x^2-356=0$ $\displaystyle x = 2\sqrt{89}$
Last edited by e^(i*pi); Mar 23rd 2009 at 04:21 PM. Reason: oops 4^4 = 256 not 16
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