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受欢迎的代数 >

7x+120=x^2

解答

7 x + 120 = x^{2}

解答

x = 15, x = - 8

求解步骤

7 x + 120 = x^{2}

交换两边

x^{2} = 7 x + 120

将

120

para o lado esquerdo

x^{2} - 120 = 7 x

将

7 x

para o lado esquerdo

x^{2} - 120 - 7 x = 0

改写成标准形式

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

x^{2} - 7 x - 120 = 0

使用求根公式求解

x_{1, 2} = \frac{- ( - 7 ) \pm ( - 7 ) ^{2} - 4 \cdot 1 \cdot ( - 120 )}{2 \cdot 1}

(- 7)^{2} - 4 \cdot 1 \cdot (- 120) = 23

x_{1, 2} = \frac{- ( - 7 ) \pm 23}{2 \cdot 1}

将解分隔开

x_{1} = \frac{- ( - 7 ) + 23}{2 \cdot 1}, x_{2} = \frac{- ( - 7 ) - 23}{2 \cdot 1}

x = \frac{- ( - 7 ) + 23}{2 \cdot 1} : 15

x = \frac{- ( - 7 ) - 23}{2 \cdot 1} : - 8

二次方程组的解是:

x = 15, x = - 8

作图

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