MQ88 --- Root of Equation

2013-07-21 5:12 am
MQ88 --- Root of EquationDifficult: 45% Show that 3x⁴ + 2x² + 3x + 1 = 0 has no real solution.

回答 (3)

2013-07-21 5:56 am
✔ 最佳答案
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2013-07-20 22:48:47 補充:
有很多方法啊,又例如:
(√3 x^2-√3/6)^2+(√3 x+√3/2)^2+1/6

2013-07-20 23:04:48 補充:
其中 (√3 x^2 - a)^2 中 0.07594 < a < 0.7015

2013-07-21 08:16:40 補充:
另一例:
(√3 x^2-√3/3)^2+(2x+3/4)^2+5/48

2013-07-21 08:35:31 補充:
又如:
(√3 x^2-√3/9)^2+((2√6)/3 x+(3√6)/8)^2+103/864

2013-07-22 20:21:43 補充:
把方法重寫:
3(x^2-1/6)^2+3(x+1/2)^2+1/6
3(x^2-1/3)^2+(2x+3/4)^2+5/48
3(x^2-1/9)^2+6(2/3 x+3/8)^2+103/864
2x^4+(x^2-1/2)^2+3(x+1/2)^2
2013-07-28 8:24 pm
3x⁴ + 2x² + 3x + 1
=3(x⁴+x²/4+3x/4+1/4)+(5x²/4+3x/4+1/4)
=3(x²+x+1/4)(x²-x+1)+(5x²+3x+1)/4
>0
2013-07-21 6:21 am
lim(x->inf)[3x⁴ + 2x² + 3x + 1]=inf
lim(x->-inf)[3x⁴ + 2x² + 3x + 1]=inf
所以如果3點本地[最高最低點]不低於0
3x⁴ + 2x² + 3x + 1 > 0
f(x)=3x⁴ + 2x² + 3x + 1
f'(x)=12x^3+4x+ 3
我計數機有3次方程~.~(奸)
x=-0.459...得一個(實數)
姐是代1個~.~(奸笑)
For x=-0.459...
f(x)=0.17752...>0(最低點)

所以呢嘿嘿嘿
3x⁴ + 2x² + 3x + 1 > 0.17752>0

2013-07-20 22:35:55 補充:
所以NO REAL SOLUTION=.=


收錄日期: 2021-04-13 19:34:26
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