Question 1209115
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When the leading coefficient of a quadratic equation is 1, then,
according to Vieta's theorem, the sum of the roots is the coefficient at x with the opposite sign,
and the product of the roots is the constant term.


Wilma's roots 5 and 15 produce the correct constant term 5*15 = 75.


Greg's roots produce the correct coefficient at x  -(-5+(-7)) = -(-5-7) = -(-12) = 12.


So, the correct equation is

    x^2 + 12x + 75 = 0.


Its roots are complex numbers

    {{{x[1,2]}}} = {{{(-12 +- sqrt(12^2 - 4*1*75))/2}}} = {{{(-12 +- sqrt(-156))/2}}} = {{{-6 +- i*sqrt(39)}}}.
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Solved.