Rút gọn biểu thức: a) M = 1/(x+2) + 2/(x-2) - 2x/(x^2-4)

* Hướng dẫn giải

a) MTC = (x -2)(x + 2). Ta rút gọn được $\mathrm{M}=\frac{1}{\mathrm{x}-2}$ 

b) Gợi ý: ${\mathrm{x}}^2+5\mathrm{x}+6=(\mathrm{x}+2)(\mathrm{x}+3);$${\mathrm{x}}^2+\mathrm{x}-12=(\mathrm{x}-3)(\mathrm{x}+4)$

Ta có $\mathrm{N}=\frac{(\mathrm{x}+2)(\mathrm{x}+3)}{(\mathrm{x}-3)(\mathrm{x}+4)}:\frac{{(\mathrm{x}+2)}^2}{\mathrm{x}(\mathrm{x}-3)}$$=\frac{\mathrm{x}(\mathrm{x}+3)}{(\mathrm{x}+2)(\mathrm{x}+4)}$