SOLUTION: 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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Question 1027293: 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.
Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
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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.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

log%282%2C%28x%29%29 + log%282%2C%28x%2B7%29%29 = 3,   --->

log%282%2C%28x%2A%28x%2B7%29%29%29 = 3,   ---> 

x*(x+7) = 2%5E3,   --->

x%5E2+%2B+7x = 8,   --->

x%5E2+%2B+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.