展开 ((3x-y)^2)/(81)

解答

展开

\frac{( 3 x - y ) ^{2}}{81}

\frac{x ^{2}}{9} - \frac{2 x y}{27} + \frac{y ^{2}}{81}

求解步骤

\frac{( 3 x - y ) ^{2}}{81}

(3 x - y)^{2} = 9 x^{2} - 6 x y + y^{2}

= \frac{9 x ^{2} - 6 x y + y ^{2}}{81}

使用分式法则:

\frac{a \pm b}{c} = \frac{a}{c} \pm \frac{b}{c}

\frac{9 x ^{2} - 6 x y + y ^{2}}{81} = \frac{9 x ^{2}}{81} - \frac{6 x y}{81} + \frac{y ^{2}}{81}

= \frac{9 x ^{2}}{81} - \frac{6 x y}{81} + \frac{y ^{2}}{81}

消掉

\frac{9 x ^{2}}{81} : \frac{x ^{2}}{9}

= \frac{x ^{2}}{9} - \frac{6 x y}{81} + \frac{y ^{2}}{81}

消掉

\frac{6 x y}{81} : \frac{2 x y}{27}

= \frac{x ^{2}}{9} - \frac{2 x y}{27} + \frac{y ^{2}}{81}

e x p an d \frac{x ^{3}}{2 ( x ^{2} - 4 )}

e x p an d sin (x) sec (x)

e x p an d \frac{5 ( 8845 - 5 )}{49}

e x p an d \frac{2 ( a + h )}{( a + h ) - 3}

e x p an d \frac{2 ( 8885 - 45 )}{49}