Question 191774This question is from textbook saxon algebra 2
: logx+log(x+1)=log20
x=5
Am I correct?
This question is from textbook saxon algebra 2
Answer by RAY100(1637)   (Show Source):
You can put this solution on YOUR website! adding logs is multiply
x(x+1) = 20
x^2 +x -20 =0
(x+5) (x-4) =0
x= (-5), (+4) but we need to check
log(4) +log(4+1) = log 20
.602 +.699=1.30 ok therefore x=+4 is valid
however when we start log (-5) etc we find again that there are no logs for negative numbers
therefore x= (-5) is not valid
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