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受欢迎的代数 >

(x+5)(x+8)=180

解答

(x + 5) (x + 8) = 180

解答

x = 7, x = - 20

求解步骤

(x + 5) (x + 8) = 180

展开

(x + 5) (x + 8) : x^{2} + 13 x + 40

x^{2} + 13 x + 40 = 180

将

180

para o lado esquerdo

x^{2} + 13 x - 140 = 0

使用求根公式求解

x_{1, 2} = \frac{- 13 \pm 1 3 ^{2} - 4 \cdot 1 \cdot ( - 140 )}{2 \cdot 1}

1 3^{2} - 4 \cdot 1 \cdot (- 140) = 27

x_{1, 2} = \frac{- 13 \pm 27}{2 \cdot 1}

将解分隔开

x_{1} = \frac{- 13 + 27}{2 \cdot 1}, x_{2} = \frac{- 13 - 27}{2 \cdot 1}

x = \frac{- 13 + 27}{2 \cdot 1} : 7

x = \frac{- 13 - 27}{2 \cdot 1} : - 20

二次方程组的解是:

x = 7, x = - 20

作图

流行的例子

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4 x^{2} - 2.90827 x + 0.528679 = 0

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x^{2} + 27 x - 160 = 0

6 t^{2} + 12 t - 210 = 0