Question 1045482
{{{system(x+y=7,xy=-5)}}}


{{{y=7-x}}}
-
{{{x(7-x)=-5}}}
{{{7x-x^2=-5}}}
{{{7x-x^2+5=0}}}
{{{-x^2+7x+5=0}}}
{{{x^2-7x-5=0}}}


{{{x=(7+- sqrt(49+4*5))/2}}}
{{{highlight(x=(7+- sqrt(69))/2)}}}


{{{xy=-5}}}
{{{y=-5/x}}}
{{{y=-5/((7+- sqrt(69))/2)}}}
{{{highlight(y=-10/(7+- sqrt(69)))}}}


The plus form for the x goes with the plus-form for y;
the minus form for x goes with the minus-form for y;
and THEN simplify in each case, the expression for y, or to rationalize the denominator.