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受欢迎的代数 >

(7+2x)(3+2x)-21=56

解答

(7 + 2 x) (3 + 2 x) - 21 = 56

解答

x = 2, x = - 7

求解步骤

(7 + 2 x) (3 + 2 x) - 21 = 56

展开

(7 + 2 x) (3 + 2 x) - 21 : 4 x^{2} + 20 x

4 x^{2} + 20 x = 56

将

56

para o lado esquerdo

4 x^{2} + 20 x - 56 = 0

使用求根公式求解

x_{1, 2} = \frac{- 20 \pm 2 0 ^{2} - 4 \cdot 4 ( - 56 )}{2 \cdot 4}

2 0^{2} - 4 \cdot 4 (- 56) = 36

x_{1, 2} = \frac{- 20 \pm 36}{2 \cdot 4}

将解分隔开

x_{1} = \frac{- 20 + 36}{2 \cdot 4}, x_{2} = \frac{- 20 - 36}{2 \cdot 4}

x = \frac{- 20 + 36}{2 \cdot 4} : 2

x = \frac{- 20 - 36}{2 \cdot 4} : - 7

二次方程组的解是:

x = 2, x = - 7

作图

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