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受欢迎的代数 >

84= 1/2 x(3x+3)

解答

84 = \frac{1}{2} x (3 x + 3)

解答

x = 7, x = - 8

求解步骤

84 = \frac{1}{2} x (3 x + 3)

在两边乘以

2

168 = x (3 x + 3)

展开

x (3 x + 3) : 3 x^{2} + 3 x

168 = 3 x^{2} + 3 x

交换两边

3 x^{2} + 3 x = 168

将

168

para o lado esquerdo

3 x^{2} + 3 x - 168 = 0

使用求根公式求解

x_{1, 2} = \frac{- 3 \pm 3 ^{2} - 4 \cdot 3 ( - 168 )}{2 \cdot 3}

3^{2} - 4 \cdot 3 (- 168) = 45

x_{1, 2} = \frac{- 3 \pm 45}{2 \cdot 3}

将解分隔开

x_{1} = \frac{- 3 + 45}{2 \cdot 3}, x_{2} = \frac{- 3 - 45}{2 \cdot 3}

x = \frac{- 3 + 45}{2 \cdot 3} : 7

x = \frac{- 3 - 45}{2 \cdot 3} : - 8

二次方程组的解是:

x = 7, x = - 8

作图

流行的例子

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