Question 371941
{{{log(10,(x))+log(10,(x+21))=2)}}}
{{{log(10,(x(x+21)))=2)}}}
{{{x(x+21)=10^2}}}
{{{x^2+21x=100}}}
{{{x^2+21x-100=0}}}
{{{(x+25)(x-4)=0}}}
Two solutions but only the positive value is allowed because the log function requires positive arguments.
{{{x-4=0}}}
{{{highlight(x=4)}}}