zs

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

受欢迎的代数 >

3+7+11+(4n-1)=n(2n+1)

解答

3 + 7 + 11 + (4 n - 1) = n (2 n + 1)

解答

n = 4, n = - \frac{5}{2}

+1

十进制

n = 4, n = - 2.5

求解步骤

3 + 7 + 11 + (4 n - 1) = n (2 n + 1)

展开

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

4 n + 20 = 2 n^{2} + n

交换两边

2 n^{2} + n = 4 n + 20

将

20

para o lado esquerdo

2 n^{2} + n - 20 = 4 n

将

4 n

para o lado esquerdo

2 n^{2} - 3 n - 20 = 0

使用求根公式求解

n_{1, 2} = \frac{- ( - 3 ) \pm ( - 3 ) ^{2} - 4 \cdot 2 ( - 20 )}{2 \cdot 2}

(- 3)^{2} - 4 \cdot 2 (- 20) = 13

n_{1, 2} = \frac{- ( - 3 ) \pm 13}{2 \cdot 2}

将解分隔开

n_{1} = \frac{- ( - 3 ) + 13}{2 \cdot 2}, n_{2} = \frac{- ( - 3 ) - 13}{2 \cdot 2}

n = \frac{- ( - 3 ) + 13}{2 \cdot 2} : 4

n = \frac{- ( - 3 ) - 13}{2 \cdot 2} : - \frac{5}{2}

二次方程组的解是:

n = 4, n = - \frac{5}{2}

作图

流行的例子

7 - x^{2} = 0

6x^4+4x^2-3x+2=2x^2(3x^2-1)

6 x^{4} + 4 x^{2} - 3 x + 2 = 2 x^{2} (3 x^{2} - 1)

6 k^{2} - 5 k - 6 = 0

5x^2-49x+421=x^2+7x-3

5 x^{2} - 49 x + 421 = x^{2} + 7 x - 3

x^{2} + 30 = 5