Question 950449
Using general solution for quadratic equation.
D1 and D2 are the discriminants of each equation.



E1, {{{D1=169-4*2*21=1}}}


E2, {{{D2=81+4*2*56=529=23^2}}}


E1,  {{{x=(13+- 1)/4}}}
{{{x=12/4}}} or {{{14/4}}}
{{{x=3}}}  or {{{x=3&1/2}}}


E2, {{{x=(-9+- 23)/4}}}
{{{x=14/4}}}  or  {{{x=-32/4}}}
{{{x=3&1/2}}}  or  {{{x=-8}}}


Common to both equations,  {{{highlight(3&1/2)}}}