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受欢迎的代数 >

0.7x^2-4.2x-0.7=0

解答

0.7 x^{2} - 4.2 x - 0.7 = 0

解答

x = 3 + 10, x = 3 - 10

+1

十进制

x = 6.16227 \dots, x = - 0.16227 \dots

求解步骤

0.7 x^{2} - 4.2 x - 0.7 = 0

在两边乘以

10

7 x^{2} - 42 x - 7 = 0

使用求根公式求解

x_{1, 2} = \frac{- ( - 42 ) \pm ( - 42 ) ^{2} - 4 \cdot 7 ( - 7 )}{2 \cdot 7}

(- 42)^{2} - 4 \cdot 7 (- 7) = 1410

x_{1, 2} = \frac{- ( - 42 ) \pm 14 10}{2 \cdot 7}

将解分隔开

x_{1} = \frac{- ( - 42 ) + 14 10}{2 \cdot 7}, x_{2} = \frac{- ( - 42 ) - 14 10}{2 \cdot 7}

x = \frac{- ( - 42 ) + 14 10}{2 \cdot 7} : 3 + 10

x = \frac{- ( - 42 ) - 14 10}{2 \cdot 7} : 3 - 10

二次方程组的解是:

x = 3 + 10, x = 3 - 10

作图

流行的例子

- 4 x^{2} + 225 = 45

4 x^{2} + 4 (2 x + 1) = 0

- x^{2} - 56 = 0

0 = - 3 x^{2} + 2 x + 1

-2.1y^2+8.04y=7.4

- 2.1 y^{2} + 8.04 y = 7.4