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受欢迎的代数 >

n/2 (25+(n-1)(-6))=-20

解答

\frac{n}{2} (25 + (n - 1) (- 6)) = - 20

解答

n = - \frac{- 31 + 1921}{12}, n = \frac{31 + 1921}{12}

+1

十进制

n = - 1.06910 \dots, n = 6.23576 \dots

求解步骤

\frac{n}{2} (25 + (n - 1) (- 6)) = - 20

在两边乘以

2

n (25 - 6 (n - 1)) = - 40

展开

n (25 - 6 (n - 1)) : - 6 n^{2} + 31 n

- 6 n^{2} + 31 n = - 40

将

40

para o lado esquerdo

- 6 n^{2} + 31 n + 40 = 0

使用求根公式求解

n_{1, 2} = \frac{- 31 \pm 3 1 ^{2} - 4 ( - 6 ) \cdot 40}{2 ( - 6 )}

3 1^{2} - 4 (- 6) \cdot 40 = 1921

n_{1, 2} = \frac{- 31 \pm 1921}{2 ( - 6 )}

将解分隔开

n_{1} = \frac{- 31 + 1921}{2 ( - 6 )}, n_{2} = \frac{- 31 - 1921}{2 ( - 6 )}

n = \frac{- 31 + 1921}{2 ( - 6 )} : - \frac{- 31 + 1921}{12}

n = \frac{- 31 - 1921}{2 ( - 6 )} : \frac{31 + 1921}{12}

二次方程组的解是:

n = - \frac{- 31 + 1921}{12}, n = \frac{31 + 1921}{12}

作图

流行的例子

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(x+2)^2(x+5)(x+9)<0

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f a c t or (x - 3 y)^{2} - (y - x)^{2}

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