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受欢迎的代数 >

0=-0.04x^2+0.8x+9

解答

0 = - 0.04 x^{2} + 0.8 x + 9

解答

x = - 5 (13 - 2), x = 5 (2 + 13)

+1

十进制

x = - 8.02775 \dots, x = 28.02775 \dots

求解步骤

0 = - 0.04 x^{2} + 0.8 x + 9

在两边乘以

100

0 = - 4 x^{2} + 80 x + 900

交换两边

- 4 x^{2} + 80 x + 900 = 0

使用求根公式求解

x_{1, 2} = \frac{- 80 \pm 8 0 ^{2} - 4 ( - 4 ) \cdot 900}{2 ( - 4 )}

8 0^{2} - 4 (- 4) \cdot 900 = 4013

x_{1, 2} = \frac{- 80 \pm 40 13}{2 ( - 4 )}

将解分隔开

x_{1} = \frac{- 80 + 40 13}{2 ( - 4 )}, x_{2} = \frac{- 80 - 40 13}{2 ( - 4 )}

x = \frac{- 80 + 40 13}{2 ( - 4 )} : - 5 (13 - 2)

x = \frac{- 80 - 40 13}{2 ( - 4 )} : 5 (2 + 13)

二次方程组的解是:

x = - 5 (13 - 2), x = 5 (2 + 13)

作图

流行的例子

x^{2} - 10 = 4 x + 11

x^{2} - 10 x + 45 = 0

0 = 12 x^{2} - 28 x + 12

(4 - x) (1 - x) + 2 = 0

2z^2+2.5z+3.75=0

2 z^{2} + 2.5 z + 3.75 = 0