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受欢迎的代数 >

x^2-20x+72=0

解答

x^{2} - 20 x + 72 = 0

解答

x = 2 (5 + 7), x = 2 (5 - 7)

+1

十进制

x = 15.29150 \dots, x = 4.70849 \dots

求解步骤

x^{2} - 20 x + 72 = 0

使用求根公式求解

x_{1, 2} = \frac{- ( - 20 ) \pm ( - 20 ) ^{2} - 4 \cdot 1 \cdot 72}{2 \cdot 1}

(- 20)^{2} - 4 \cdot 1 \cdot 72 = 47

x_{1, 2} = \frac{- ( - 20 ) \pm 4 7}{2 \cdot 1}

将解分隔开

x_{1} = \frac{- ( - 20 ) + 4 7}{2 \cdot 1}, x_{2} = \frac{- ( - 20 ) - 4 7}{2 \cdot 1}

x = \frac{- ( - 20 ) + 4 7}{2 \cdot 1} : 2 (5 + 7)

x = \frac{- ( - 20 ) - 4 7}{2 \cdot 1} : 2 (5 - 7)

二次方程组的解是:

x = 2 (5 + 7), x = 2 (5 - 7)

作图

流行的例子

2 x^{2} + 7 x + 2 = - 1

11 x^{2} = 7 - 2 x

2 t^{2} + 2 t - 1 = 0

4 X^{2} + 5 X - 51 = 0

4 x^{2} - 20 x = - 45