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The following equation represents two straight lines. Determine the equation of each of the two lines.

x^2+8 xy−x+16 y^2−4 y−72=0

I know we need to take common factors and the answer is

(x+4 y-9) (x+4 y+8) = 0

leading to equations y = 1/4 (-x-8) and y = (9-x)/4 but how did we get to (x+4 y-9) (x+4 y+8) = 0 in the first place?? Thanks

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# How to find equations of two lines given a conic equation?

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