Question

bai 1, tim x thuoc Z, biet

a,3a+2 chia hết cho x-1

b, x^2 +2 * x - 7 chia hết cho x+2

c, x^2 + x + 1 chia hết cho x+1

d, 32-8 chia hết cho x- 4

e, x+5 chia hết cho x-2

g, 2x chia hết cho x-1

Answer 1

b: \(x^2+2x-7⋮x+2\)

\(\Leftrightarrow x\left(x+2\right)-7⋮x+2\)

\(\Leftrightarrow x+2\in\left\{1;-1;7;-7\right\}\)

hay \(x\in\left\{-1;-3;5;-9\right\}\)

c: \(x^2+x+1⋮x+1\)

\(\Leftrightarrow x\left(x+1\right)+1⋮x+1\)

\(\Leftrightarrow x+1\in\left\{1;-1\right\}\)

hay \(x\in\left\{0;-2\right\}\)

e: \(x+5⋮x-2\)

\(\Leftrightarrow x-2+7⋮x-2\)

\(\Leftrightarrow x-2\in\left\{1;-1;7;-7\right\}\)

hay \(x\in\left\{3;1;9;-5\right\}\)