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# Algebra

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Marina solved the quadratic equation 9x^2-18x-720=8x^2-15x-640 by completing the square. In the process, she came up with the equivalent equation (x+r)^2 = s,where r and s are constants.  What is s?

May 30, 2021

$x^2-3x-80=0$. You know that $r=-\frac{3}{2}$ so to find $s$ subtract $\left(x-\frac{3}{2}\right)^2$ from the LHS.