Question

Tim x de phan so sau co gia tri nguyen:

a) \(\frac{7-x}{x-2}\)   b)\(\frac{x+8}{3-x}\)  c)\(\frac{x^2-6x-3}{x-4}\) d)\(\frac{x^2-x+1}{x+2}\)

Ai nhanh mik tick!!!

Answer 1

a) Để \(\frac{7-x}{x-2}\inℤ\) thì \(\left(7-x\right)⋮\left(x-2\right)\)

\(\Leftrightarrow\left[-1\left(7-x\right)\right]⋮\left(x-2\right)\)

\(\Leftrightarrow\left[x-7\right]⋮\left(x-2\right)\)

\(\Leftrightarrow\left[x-2-5\right]⋮\left(x-2\right)\)

Vì \(\Leftrightarrow\left[x-2\right]⋮\left(x-2\right)\) nên \(\Leftrightarrow5⋮\left(x-2\right)\)

hay \(x-2\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)

Lập bảng:

\(x-2\)	\(1\)	\(-1\)	\(5\)	\(-5\)
\(x\)	\(3\)	\(1\)	\(7\)	\(-3\)

Vậy \(x\in\left\{1;\pm3;7\right\}\)

Answer 2

b) Để \(\frac{x+8}{3-x}\inℤ\) thì \(\left(x+8\right)⋮\left(3-x\right)\)

\(\Leftrightarrow\left[-1\left(x+8\right)\right]⋮\left(3-x\right)\)

\(\Leftrightarrow\left[8-x\right]⋮\left(3-x\right)\)

\(\Leftrightarrow\left[5+3-x\right]⋮\left(3-x\right)\)

Vì \(\left[3-x\right]⋮\left(3-x\right)\) nên \(5⋮\left(3-x\right)\)

Lập bảng như câu a)

Answer 3

Vay ban co biet lam phan c va d ko?