Question 901709
{{{ax-a(a+b)=-x-(1+ab)}}}
{{{ax+x=a(a+b)-(1+ab)}}}
{{{x(a+1)=a^2+ab-1-ab}}}
{{{x(a+1)=a^2-1}}
{{{x(a+1)=(a+1)(a-1)}}}
{{{highlight(x=a-1)}}}