Tìm x thuộc Z:a, -2x-11 chia hết cho 3x+2 b, 2.(x-3)-3.(x-5)=2.(3-x)-18

Đáp án:

a) −2x−11⋮3x+2

⇔−6x−33⋮3x+2

⇔−2(3x+2)−29⋮3x+2

⇔29⋮3x+2

⇒x∈{−1;9}

b) 2(x−3)−3.(x−5)=4(3−x)−18

⇒2x−6−3x+15=12−4x−18

⇒2x−3x+4x=12−18+6−15

⇒3x=−15

⇒x=−5