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受欢迎的代数 >

1+0.4x-0.21x^2=0

解答

1 + 0.4 x - 0.21 x^{2} = 0

解答

x = - \frac{10}{7}, x = \frac{10}{3}

+1

十进制

x = - 1.42857 \dots, x = 3.33333 \dots

求解步骤

1 + 0.4 x - 0.21 x^{2} = 0

在两边乘以

100

100 + 40 x - 21 x^{2} = 0

改写成标准形式

a x^{2} + b x + c = 0

- 21 x^{2} + 40 x + 100 = 0

使用求根公式求解

x_{1, 2} = \frac{- 40 \pm 4 0 ^{2} - 4 ( - 21 ) \cdot 100}{2 ( - 21 )}

4 0^{2} - 4 (- 21) \cdot 100 = 100

x_{1, 2} = \frac{- 40 \pm 100}{2 ( - 21 )}

将解分隔开

x_{1} = \frac{- 40 + 100}{2 ( - 21 )}, x_{2} = \frac{- 40 - 100}{2 ( - 21 )}

x = \frac{- 40 + 100}{2 ( - 21 )} : - \frac{10}{7}

x = \frac{- 40 - 100}{2 ( - 21 )} : \frac{10}{3}

二次方程组的解是:

x = - \frac{10}{7}, x = \frac{10}{3}

作图

流行的例子

0 = - x^{2} + x

solvefor x,b^2x^2-a^2y^2=3a^2b^2

so l v e f or x, b^{2} x^{2} - a^{2} y^{2} = 3 a^{2} b^{2}

x^{2} - 9 x - 43 = 27

G(x)=-0.003x^2+6x-1700

G (x) = - 0.003 x^{2} + 6 x - 1700

266=0.68*100*X*1.79*(4.75-0.4*X)

266 = 0.68 \cdot 100 \cdot X \cdot 1.79 \cdot (4.75 - 0.4 \cdot X)