\({5x^{2} + 6xy - 8y^{2}}\)

this is a perfect square, so i know:

\({{(a + b)^{2} = a^{2} + 2ab + b^{2}}}\)

just how would i factor this though? i'm completely lost :-(

Break the expression into groups:

(5x^2-4xy) + (10xy-8y^2).

Factor out x and 2y respectively:

x(5x-4y) + 2y(5x-4y).

Factor out common term:

(x+2y)(5x - 4y) <---- Answer

where did -4xy & 10xy come from?

i guess you can think of it in the form: ax^{2}+bx+c instead of ax^{2}+bxy+c^{2} then, factor the resulting quadratic using your methods