展开 (n-1)+((n(n-1)))/2

解答

展开

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

n - 1 + \frac{n ^{2}}{2} - \frac{n}{2}

求解步骤

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

去除括号:

(a) = a

= n - 1 + \frac{n ( n - 1 )}{2}

乘开

n (n - 1) : n^{2} - n

= n - 1 + \frac{n ^{2} - n}{2}

使用分式法则:

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

\frac{n ^{2} - n}{2} = \frac{n ^{2}}{2} - \frac{n}{2}

= n - 1 + \frac{n ^{2}}{2} - \frac{n}{2}

e x p an d \frac{2}{( x + 2 ) ( x ^{2} - 1 )}

e x p an d \frac{1}{y ( a + b y )}

e x p an d - \frac{5 ( 41 - 5 )}{7}

e x p an d \frac{2}{s ( s ^{3} + s ^{2} + 5 )}

e x p an d A (- 2, - 5) B (8, 3)