(1)
=(x^2-2x)-(5x-10)
=x(x-2)-5(x-2)
=(x-2)(x-5)
(2)
=(3x+2y)^2(a-b)-(2x-3y)^2(a-b)
=(a-b)[(3x+2y)^2-(2x-3y)^2]
=(a-b)[(3x+2y)+(2x-3y)]
[(3x+2y)-(2x-3y)]
=(a-b)(5x-y)(x+5y)