Tính: a. 9x^2/11y^2: 3x/2y: 6x/11y; b. (x^2-49)/(x-7)+x-2

* Hướng dẫn giải

a. $\frac{9x^2}{11y^2}:\frac{3x}{2y}:\frac{6x}{11y}$

$=\frac{9x^2}{11y^2}.\frac{2y}{3x}.\frac{11y}{6x}$

$=\frac{9x^2.2y.11y}{11y^2.3x.6x}$ $=1.$

b. $\frac{x^2-49}{x-7}+x-2$

$=\frac{x^2-49}{x-7}+\frac{(x-2)(x-7)}{x-7}$ $=\frac{x^2-49}{x-7}+\frac{x^2-9x+14}{x-7}$

$=\frac{x^2-49+x^2-9x+14}{x-7}$$=\frac{2x^2-9x+35}{x-7}$

$=\frac{(x-7)(2x+5)}{x-7}$