5x(x - 2)
I assume you mean 10x - 25x^2 (i.e. to the power of 2, or x squared) If so 10x - 25x^2 = 5x (2 - 5x)
(2x - 1)(5x + 8)
you don't need to factor, just straight subtraction 5x-10x=-5x
(5x - 3)(2x + 1)
2(5x + 7)(x - 5)
5x + 10x doesn't need factorization as you can just add them up (5x+10x=15x). However, if you really want to, 5x+10x=5x(1+2)=5x(3)=15x
10x^2 - x - 2 = (5x + 2)(2x - 1)
10x - 5x + 5x = 10x
(5x - 2y)(5x + 2y)
(5x-10)(x+3)
(10x-3(10x+3)