\(a,ĐK:x\ne\pm2\\ b,M=\dfrac{x^2+5x+6+x^2-5x+6-2x^2-3x-6}{\left(x-2\right)\left(x+2\right)}\\ M=\dfrac{-3x+6}{\left(x-2\right)\left(x+2\right)}=\dfrac{-3\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{-3}{x+2}\\ c,x=3\Rightarrow M=\dfrac{-3}{-3+2}=\dfrac{-3}{-1}=3\)
a) M xác định khi \(x\ne\pm2\)
b)\(\dfrac{x+3}{x-2}+\dfrac{x-3}{x+2}-\dfrac{2x^2+3x+6}{x^2-4}=\dfrac{\left(x+3\right)\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}+\dfrac{\left(x-3\right)\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}-\dfrac{2x^2+3x+6}{\left(x-2\right)\left(x+2\right)}=\dfrac{6-3x}{\left(x-2\right)\left(x+2\right)}=\dfrac{-3}{x+2}\)
c)Thấy x=3 thỏa mãn đkxđ ta thay x=3 vào biểu thức đã rút gọn ta được M=-3/5
