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受欢迎的代数 >

2x^4-81=0

解答

2 x^{4} - 81 = 0

解答

x = \frac{3}{2}, x = - \frac{3}{2}, x = - \frac{9}{2}, x = - - \frac{9}{2}

求解步骤

2 x^{4} - 81 = 0

将

81

到右边

2 x^{4} = 81

两边除以

2

x^{4} = \frac{81}{2}

用

u = x^{2}

和

u^{2} = x^{4}

改写方程式

u^{2} = \frac{81}{2}

解

u^{2} = \frac{81}{2} : u = \frac{81}{2}, u = - \frac{81}{2}

u = \frac{81}{2}, u = - \frac{81}{2}

代回

u = x^{2}

，求解

x

解

x^{2} = \frac{81}{2} : x = \frac{3}{2}, x = - \frac{3}{2}

解

x^{2} = - \frac{81}{2} : x = - \frac{9}{2}, x = - - \frac{9}{2}

解为

x = \frac{3}{2}, x = - \frac{3}{2}, x = - \frac{9}{2}, x = - - \frac{9}{2}

作图

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