Đề bài

1. $A = {{{a^2} + {b^2}} \over {{x^3} + {x^2}y}}.{{{x^2} - {y^2}} \over {{a^4} - {b^4}}}$

2. $B = {{64{x^2}{y^2} - 1} \over {{x^2} - 4}}.{{{{\left( {x + 2} \right)}^2}} \over {{x^2} - 4}}.{{{{\left( {x - 2} \right)}^2}} \over {8xy + 1}}$

3. $C = \left( {1 - {{a - b} \over {a + b}}} \right).\left( {2 + {{2b} \over {a - b}}} \right).$