Question 247920
1) x^2-8x+15=0
(x-3)*(x-5) = 0
x = 3, x = 5
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2) x^2+2x-6=0
*[invoke solve_quadratic_equation 1,2,-6]
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x = -1 ± sqrt(7)
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3) 2x^2+3x-5=0 
do these like the ones above.  If you can't factor them, use the quadratic equation.  It always works.
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4) 2x^2+7x+6=0 

4) x^2-4x+5=0

5) x^2-10x+28=0