Question 626925
Let {{{x = a + b}}} 
{{{(a+b)^2 - 4(a+b) + 3}}} = {{{ x^2 - 4x + 3}}}
                           = {{{ (x-3)(x-1) }}}, substitute {{{x = a + b}}}
                           = {{{highlight((a+b-3)(a+b-1))}}}