展开 (3n(3n+1))/2

解答

展开

\frac{3 n ( 3 n + 1 )}{2}

\frac{9 n ^{2}}{2} + \frac{3 n}{2}

求解步骤

\frac{3 n ( 3 n + 1 )}{2}

乘开

3 n (3 n + 1) : 9 n^{2} + 3 n

= \frac{9 n ^{2} + 3 n}{2}

使用分式法则:

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

\frac{9 n ^{2} + 3 n}{2} = \frac{9 n ^{2}}{2} + \frac{3 n}{2}

= \frac{9 n ^{2}}{2} + \frac{3 n}{2}

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