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受欢迎的代数 >

n^2=18n+40

解答

n^{2} = 18 n + 40

解答

n = 20, n = - 2

求解步骤

n^{2} = 18 n + 40

将

40

para o lado esquerdo

n^{2} - 40 = 18 n

将

18 n

para o lado esquerdo

n^{2} - 40 - 18 n = 0

改写成标准形式

a x^{2} + b x + c = 0

n^{2} - 18 n - 40 = 0

使用求根公式求解

n_{1, 2} = \frac{- ( - 18 ) \pm ( - 18 ) ^{2} - 4 \cdot 1 \cdot ( - 40 )}{2 \cdot 1}

(- 18)^{2} - 4 \cdot 1 \cdot (- 40) = 22

n_{1, 2} = \frac{- ( - 18 ) \pm 22}{2 \cdot 1}

将解分隔开

n_{1} = \frac{- ( - 18 ) + 22}{2 \cdot 1}, n_{2} = \frac{- ( - 18 ) - 22}{2 \cdot 1}

n = \frac{- ( - 18 ) + 22}{2 \cdot 1} : 20

n = \frac{- ( - 18 ) - 22}{2 \cdot 1} : - 2

二次方程组的解是:

n = 20, n = - 2

作图

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