Question 365171
Joe thought of two numbers, their sum was 20 and the sum of their squares was 300. What is their product? 
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Use x and y
x + y = 20
{{{x^2 + y^2 = 300}}}
Sub for y: y = 20-x
{{{x^2 + (20-x)^2 = 300}}}
{{{2x^2 - 40x + 100 = 0}}}
{{{x^2 - 20x + 50 = 0}}}
*[invoke solve_quadratic_equation 1,-20,50]
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x = 10 ± 5sqrt(2)
--> x = 10 + 5sqrt(2), y = 10 - 5sqrt(2) or vice versa
The product = 100 - 50 = 50