展开 (q(L-x)*(L+2x))/6

解答

展开

\frac{q ( L - x ) \cdot ( L + 2 x )}{6}

\frac{q L ^{2}}{6} + \frac{q Lx}{6} - \frac{q x ^{2}}{3}

求解步骤

\frac{q ( L - x ) ( L + 2 x )}{6}

乘开

q (L - x) (L + 2 x) : q L^{2} + q Lx - 2 q x^{2}

= \frac{q L ^{2} + q Lx - 2 q x ^{2}}{6}

使用分式法则:

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

\frac{q L ^{2} + q Lx - 2 q x ^{2}}{6} = \frac{q L ^{2}}{6} + \frac{q Lx}{6} - \frac{2 q x ^{2}}{6}

= \frac{q L ^{2}}{6} + \frac{q Lx}{6} - \frac{2 q x ^{2}}{6}

消掉

\frac{2 q x ^{2}}{6} : \frac{q x ^{2}}{3}

= \frac{q L ^{2}}{6} + \frac{q Lx}{6} - \frac{q x ^{2}}{3}

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