展开 (4(3^n-1))/3

解答

展开

\frac{4 ( 3 ^{n} - 1 )}{3}

4 \cdot 3^{n - 1} - \frac{4}{3}

求解步骤

\frac{4 ( 3 ^{n} - 1 )}{3}

乘开

4 (3^{n} - 1) : 4 \cdot 3^{n} - 4

= \frac{4 \cdot 3 ^{n} - 4}{3}

使用分式法则:

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

\frac{4 \cdot 3 ^{n} - 4}{3} = \frac{4 \cdot 3 ^{n}}{3} - \frac{4}{3}

= \frac{4 \cdot 3 ^{n}}{3} - \frac{4}{3}

消掉

\frac{4 \cdot 3 ^{n}}{3} : 4 \cdot 3^{n - 1}

= 4 \cdot 3^{n - 1} - \frac{4}{3}

e x p an d (3 x^{2} + 5) ln (2)

e x p an d \frac{p}{( ( p ^{2} + 4 ) ( p ^{2} + 9 ) )}

e x p an d t^{b} a + \frac{d}{d x} (3 x^{2} (7 - x)^{5})

e x p an d ((A x + B) e^{x}) x

\frac{d}{d t} ((x) (2 x - 1))