How do you factor y^2 + 2xy - 63x^2 ?

1 Answer
May 17, 2015

Consider (y+ax)(y-bx) = y^2+(a-b)y-(ab)x^2

Comparing coefficients with our target quadratic, we are looking for a and b such that a - b = 2 and ab=63.

Well 63 = 9*7 and 9-7 = 2

Hence y^2+2xy-63x^2 = (y+9x)(y-7x)