Đáp án + Giải thích các bước giải:
`b)` `(x + 1)/(x + 2) + 5/(x-2) = 4/(x^2-4)+1(đkxđ:xnepm2)` $\\$ `<=> [(x+1)(x-2)]/[(x+2)(x-2)]=4/[(x-2)(x+2)]+[(x-2)(x+2)]/[(x-2)(x+2)]` $\\$ `<=> [(x+1)(x-2)]/[(x+2)(x-2)] = [4 + (x-2)(x+2)]/[(x-2)(x+2)]` $\\$ `=> (x+1)(x-2) = 4 + (x - 2)(x+2) <=> x^2 - 2x+x-2=4+x^2-4` $\\$ `<=> x^2 - 2x + x - 2 - 4 - x^2 = -4` $\\$ `<=> -x - 6=-4 <=> -x = 2<=>x=-2(ktmđk)`
Vậy `S = emptyset`
`c)` `(x + 2)/3 >= (2x-1)/4 - 1` $\\$ `<=> 12*(x+2)/3>=12*(2x-1)/4-12*1` $\\$ `<=> 4(x+2) >= 3(2x - 1) - 12` $\\$ `<=> 4x + 8 >= 6x - 3 - 12` $\\$ `<=> 4x + 8 >= 6x - 15` $\\$ `<=> 4x - 6x >= -15 - 8` $\\$ `<=> -2x >= -23` $\\$ `<=> x <= 23/2`
Vậy `S= {x|x<=23/2}`