Question 1027293
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Hi, I'm having trouble solving and figuring what to do for this problem:

Solve    log base 2 of x + log base 2 of (x+7) = 3

Thank you.
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<pre>
{{{log(2,(x))}}} + {{{log(2,(x+7))}}} = {{{3}}},   --->

{{{log(2,(x*(x+7)))}}} = {{{3}}},   ---> 

x*(x+7) = {{{2^3}}},   --->

{{{x^2 + 7x}}} = {{{8}}},   --->

{{{x^2 + 7x - 8}}} = {{{0}}},  

Factor left side:

(x+8)*(x-1) = 0.

The roots are x=-8 and x=1.

-8 doesn't fit because of logarithm.

x=1  fits perfectly.
</pre>