Đáp án:
`a)xy-3x=-19`
`->x(y-3) = -19`
`-> x, (y-3) ∈ Ư_(-19) = {(-1,19) ; (-19, 1) ; (1,-19),(19,-1)}`
`-> (x,y) ∈ {(-1,22);(-19,4);(1,-16);(19,2)}`
Vậy `(x,y) ∈ {(-1,22);(-19,4);(1,-16);(19,2)}`
`b)3x+4y-xy=16`
`-> 3x+4y-xy - 12 = 16-12`
`-> x(3-y) - 4(3-y) = 4`
`-> (x-4)(3-y) = 4`
`-> (x-4),(3-y) ∈ Ư_(4) = {±1,±4 ; ±2,±2 }`
Bạn tự tính nốt
Vậy `(x,y) ∈ {...}`
`c)x.(x+3)=0`
`*Th1: x=0`
`*th2: x+3= 0 `
`-> x = -3`
Vậy `x ∈ {0,-3}`
`d)(x-2)(5-x)=0`
`Th1 : x-2 = 0 -> x = 2`
`Th2 :5-x = 0 -> x = 5`
Vậy `x ∈ {2,5}`
`e)(x+1)(x^2 +1)=0`
`Th1 : x+1 = 0 -> x = -1`
`Th2 : x^2 + 1 = 0 -> x ^2 = -1 -> x ∈ ∅ `
Vậy `x = -1`
`g)-12(x-5)+7(3-x)=5`
`-> -12x + 60 + 7(-x+3) = 5`
`-> -12x + 60 - 7x + 21 = 5`
`-> -12x-7x + 81 = 5`
`-> -19x = -76`
`-> x = 4`
Vậy `x=4`
`h)30(x+2)-6(x-5)-24x=100`
`-> 30x + 60−6x+30−24x=100`
`-> 30x+90−6x−24x=100`
`-> 90=100`
`-> x ∈ ∅`
Vậy `x ∈ ∅`
