Question

Answer 1

a: ĐKXĐ: x∉{3;-3}

b: \(M=\left(\frac{x}{x^2-9}+\frac{1}{x+3}+\frac{2}{3-x}\right):\frac{3}{x+3}\)

\(=\left(\frac{x}{\left.\left(x-3\right)\left(x+3\right)\right.}+\frac{1}{x+3}-\frac{2}{x-3}\right)\cdot\frac{x+3}{3}\)

\(=\frac{x+x-3-2\left(x+3\right)}{\left(x+3\right)\left(x-3\right)}\cdot\frac{x+3}{3}=\frac{2x-3-2x-6}{\left(x-3\right)\cdot3}=\frac{-9}{3\left(x-3\right)}=-\frac{3}{x-3}\)

c: Khi x=-7 thì \(M=\frac{-3}{-7-3}=\frac{-3}{-10}=\frac{3}{10}\)

d: Để M là số nguyên thì -3⋮x-3

=>x-3∈{1;-1;3;-3}

=>x∈{4;2;6;0}