Question 760715
Two numbers, h and k.
hk=15 and h+k=7


{{{h=7-k}}}, substitute into the 15 equation.
{{{(h)k=15}}}
{{{(7-k)k=15}}}
{{{7k-k^2=15}}}
{{{-k^2+7k-15=0}}}
{{{k^2-7k+15=0}}} which would have been what lead to your question.  Use the general solution to a quadratic equation.


{{{k=(7+- sqrt(49-4*15))/2}}}
{{{k=(7+- sqrt(-11))/2}}}
NO REAL SOLUTION