Question 749517
x^2+9y^2=9
-2x+1y=-3 --> y = 2x-3
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Sub for y in the 1st eqn
x^2+9y^2=9
{{{x^2 + 9*(2x-3)^2 = 9}}}
{{{x^2 + 36x^2 - 108x + 81 = 9}}}
{{{37x^2 - 108x + 72 = 0}}}
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*[invoke solve_quadratic_equation 37,-108,72]
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It might be called "elimination" since the y terms were eliminated by the substitution.