Question 354826
{{{ ln(x +7) + ln(x + 3) = ln(77)}}}
{{{ ln((x +7)(x + 3)) = ln(77)}}}
{{{(x +7)(x + 3) = 77}}}
{{{x^2+3x+7x+21=77}}}
{{{x^2+10x+21=77}}}
{{{x^2+10x=56}}}
{{{x^2+10x+25=56+25}}}
{{{(x+5)^2=81}}}
{{{x+5=0 +- 9}}}
{{{x=5 +- 9}}}
{{{x1=14}}} and {{{x2=-4}}}
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However since {{{ln(-4+3)=ln(-1)}}} is undefined, only {{{highlight(x=14)}}} is a valid solution.