Question

[lê trần minh quân]

2.Tìm x,y thuộc Z, biết

a)(x-2)(x+3)=15

b)(2x-1)(y-4)=-13

c)(x+3)chia hết cho x+1

Answer 1

[Anh2Kar六]

c)\(\Leftrightarrow\)(x+1)+2 chia hết  x+1
\(\Rightarrow\)2 chia hết x+1
\(\Rightarrow\)x+1 ∈ {1,-1,2,-2}
\(\Rightarrow\)x ∈ {0,-2,1,-3}

Answer 2

[Trần Đặng Phan Vũ]

c) \(x+3⋮x+1\)

\(\Rightarrow x+1+2⋮x+1\)

\(\Rightarrow2⋮x+1\) ( vì \(x+1⋮x+1\) )

\(\Rightarrow x+1\in\text{Ư}_{\left(2\right)}\)

\(\text{Ư}_{\left(2\right)}=\text{ }\left\{1;-1;2;-2\right\}\)

\(x+1\)	\(1\)	\(-1\)	\(2\)	\(-2\)
\(x\)	\(0\)	\(-2\)	\(1\)	\(-3\)

vậy................