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受欢迎的代数 >

completesquare x^2-4/5 x-4

解答

配方

x^{2} - \frac{4}{5} x - 4

解答

(x - \frac{2}{5})^{2} - \frac{104}{25}

求解步骤

x^{2} - \frac{4}{5} x - 4

改写成标准形式

a x^{2} + b x + c

x^{2} - \frac{4 x}{5} - 4

将

x^{2} - \frac{4 x}{5} - 4

改写为如下形式:

x^{2} + 2 a x + a^{2}

2 a = - \frac{4}{5} : a = - \frac{2}{5}

加和减

(- \frac{2}{5})^{2}

x^{2} - \frac{4 x}{5} - 4 + (- \frac{2}{5})^{2} - (- \frac{2}{5})^{2}

x^{2} + 2 a x + a^{2} = (x + a)^{2}

x^{2} - \frac{4}{5} x + (- \frac{2}{5})^{2} = (x - \frac{2}{5})^{2}

(x - \frac{2}{5})^{2} - 4 - (- \frac{2}{5})^{2}

化简

(x - \frac{2}{5})^{2} - \frac{104}{25}

作图

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