How do you solve lnx + ln (x-2) = 1lnx+ln(x2)=1?

1 Answer
Sep 1, 2016

x = 1 + sqrt(1 + e)x=1+1+e

Explanation:

Start by applying the rule log_a(n) + log_a(m) = log_a(n xx m)loga(n)+loga(m)=loga(n×m).

ln(x(x - 2)) = 1ln(x(x2))=1

ln(x^2 - 2x) = 1ln(x22x)=1

x^2 - 2x = e^1x22x=e1

x^2 - 2x = ex22x=e

x^2 - 2x - e = 0x22xe=0

Solve by the quadratic formula.

x = (-(-2) +- sqrt(-2^2 - (4 xx 1 xx -e)))/(2 xx 1)x=(2)±22(4×1×e)2×1

x = (2 +- sqrt(4 + 4e))/2x=2±4+4e2

x = (2 +- sqrt(4(1 + e)))/2x=2±4(1+e)2

x = (2 +- 2sqrt(1 + e))/2x=2±21+e2

x = 1 +- sqrt(1 + e)x=1±1+e

However, the - solution is extraneous, since it renders the original equation undefined. So, the only actual solution is x = 1+sqrt(1 + e)x=1+1+e

Hopefully this helps!