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受欢迎的代数 >

completesquare x^2-0.4x-1.2=0

解答

x^{2} - 0.4 x - 1.2 = 0

解答

x = \frac{31 + 1}{5}, x = \frac{- 31 + 1}{5}

+1

十进制

x = 1.31355 \dots, x = - 0.91355 \dots

求解步骤

x^{2} - 0.4 x - 1.2 = 0

在两边乘以

10

10 x^{2} - 4 x - 12 = 0

将

12

到右边

10 x^{2} - 4 x = 12

两边除以

10

\frac{10 x ^{2} - 4 x}{10} = \frac{12}{10}

x^{2} - \frac{2 x}{5} = \frac{6}{5}

改写为形式

(x + a)^{2} = b

(x - \frac{1}{5})^{2} = \frac{31}{25}

若

f^{2} (x) = a

，解为

f (x) = a, - a

解

x - \frac{1}{5} = \frac{31}{25} : x = \frac{31 + 1}{5}

解

x - \frac{1}{5} = - \frac{31}{25} : x = \frac{- 31 + 1}{5}

二次方程组的解是:

x = \frac{31 + 1}{5}, x = \frac{- 31 + 1}{5}

作图

流行的例子

solvefor D,(x^2D^2-4xD-6I)y=0

so l v e f or D, (x^{2} D^{2} - 4 x D - 6 I) y = 0

(x - 2)^{2} = 8 (x - 2)

3 x^{2} + 52 x - 256 = 0

(x + 3)^{2} = x + 15

0 = 1 + x^{2}