Question

e cần gấp ạ

Answer 1

Bài 3: 

a: \(M=\dfrac{21+\left(x-4\right)\left(x+3\right)-\left(x-1\right)\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}:\dfrac{x+3-1}{x+3}\)

\(=\dfrac{21+x^2-x-12-x^2+4x-3}{\left(x-3\right)\left(x+3\right)}\cdot\dfrac{x+3}{x+2}\)

\(=\dfrac{3x+6}{x-3}\cdot\dfrac{1}{x+2}=\dfrac{3}{x-3}\)

b: Để M<0 thì x-3<0

hay x<3

Bài 5:

a: \(A=\dfrac{2a^2-6a+3a+9-a^2-9}{\left(a-3\right)\left(a+3\right)}=\dfrac{a^2-3a}{\left(a-3\right)\left(a+3\right)}=\dfrac{a}{a+3}\)

c: Để A nguyên thì \(a+3\in\left\{1;-1;3;-3\right\}\)

hay \(a\in\left\{-2;-4;0;-6\right\}\)