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受欢迎的代数 >

9x^4-81x^2=0

解答

9 x^{4} - 81 x^{2} = 0

解答

x = 3, x = - 3, x = 0

求解步骤

9 x^{4} - 81 x^{2} = 0

用

u = x^{2}

和

u^{2} = x^{4}

改写方程式

9 u^{2} - 81 u = 0

解

9 u^{2} - 81 u = 0 : u = 9, u = 0

u = 9, u = 0

代回

u = x^{2}

，求解

x

解

x^{2} = 9 : x = 3, x = - 3

解

x^{2} = 0 : x = 0

解为

x = 3, x = - 3, x = 0

作图

流行的例子

y^{8} - 23 y = 0

(3x^2+5x-7)^4=1

(3 x^{2} + 5 x - 7)^{4} = 1

6x^4-35x^3+62x^2-35x+6=0

6 x^{4} - 35 x^{3} + 62 x^{2} - 35 x + 6 = 0

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

0 = x^{4} - 10 x^{2} + 9