Posted by **Chris** on Tuesday, December 22, 2009 at 4:26pm.

log10x + log10(x+1)=1

In other words

log base 10 + log base 10(x+1)=1

I need to show it algebraically not using calculator

Thanks a lot !

- Advanced Math -
**Reiny**, Tuesday, December 22, 2009 at 4:34pm
log10x + log10(x+1)=1

log10[x(x+1)] = 1

x(x+1) = 10^1

x^2 + x - 10 = 0

x = (-1 ± √41)/2

but for log10 x, x > 0

so x = (-1 + √41)/2

- Advanced Math -
**Chris**, Tuesday, December 22, 2009 at 4:47pm
thanks for you help and especially explanation

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