`(5x+1)(5x-2) - 10(x-10) = 25x(x+2)`
`<=> 25x^2 - 5x - 2 - (10x - 100) = 25x^2 + 50x`
`<=> 25x^2 - 5x - 2 - 10 x + 100 - 25x^2 - 50x = 0`
`<=> (25x^2 - 25x^2) - (5x + 10x + 50x) +(-2 + 100) = 0`
`<=> -65x + 98 = 0`
`<=> -65x = -98`
`<=> x = 98/65`
Vậy `x=98/65`