Đáp án:

`b) (5x + 1)/5 - (2x - 1)/(2x + 2) = 2 + (x^2 + 4x + 1)/(x + 1)`

Điều kiện : `x \ne -1`

`<=> (5x + 1)/5 - (2x - 1)/(2(x+1)) = 2 + (x^2 + 4x + 1)/(x + 1)`

`<=> ( 2(5x + 1)(x + 1) - 5(2x - 1))/(10(x+1)) = ( 20(x + 1) + 10(x^2 + 4x + 1))/(10(x + 1))`

`=> 2(5x^2+x+5x+1) - (10x - 5) = 20x + 20 + 10x^2 + 40x + 10`

`<=> 2(5x^2+6x+1) - 10x + 5 = 10x^2+60x+30`

`<=> 10x^2+12x+2-10x+5=10x^2+60x+30`

`<=> 10x^2 + 12x - 10x - 10x^2 - 60x = 30 - 5 - 2`

`<=> -58x = 23`

`<=> x = -23/58` (thỏa mãn)

Vậy `S = {-23/58}`