试说明-X方 1分之-x4次方-6x方 8的最小值为8

x²-13x+1=0两边除以xx+1/x=13两边平方可得x²+1/x²+2=169x²+1/x²=167两边平方可得x^4+1/x^4=167&su

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x的平方-13x+1=0x+1/x=13（0）（0）两边平方x^2+2+1/x^2=169x^2+1/x^2=167（1）（1）两边再平方x^4+2+1/x^4=27889则x^4+1/x^4=278

1－x分之1＋1＋x分之1＋1＋x²分之2＋1＋x4次方分之4=1－x²分之（x+1+1-x)＋1+x²分之2＋1＋x4次方分之4=1－x²分之1＋1+x

x+1/x=3,两边同时平方得到x^2+1/x^2+2=9所以x^2+1/x^2=7x^2/(x^4+x^2+1)=1/(x^2+1/x^2+1)=1/(7+1)=1/8

x^2/x^4+x^2+1=1/x^2+x^2+1x+1/x=3(x+1/x)^2=3^2=9x^2+1/x^2+2=9x^2+1/x^2=7则x^2+1/x^2+1=8即x^2/x^4+x^2+1=

x+1/x==3两边乘xx²+1=3x两边平方x^4+2x²+1=9x²x^4+x²+1=8x²所以x²/(x^4+x²+1)=1

分析：降次x^2=5x-1所以（x^4+1）/x^2=[(5x-1)^2+1]/(5x-1)=(25x^2-10x+2)/(5x-1)=[25(5x-1)-10x+2]/(5x-1)=(115x-23

X/(X^2+X+1)=a1/(x+1+1/x)=ax+1/x=1/a-1x^2+1/x^2+2=(1-a)^2/a^2x^2+1/x^2+1=(1-a)^2/a^2-1=(1-2a)/a^2X^2/

4分之x4次方y8次方-6x平方y平方+36y4次方=（1/2x²y的4次方-6y²）²如果本题有什么不明白可以追问,

原式=(x+1)//(x²+1)*(x²+1)(x+1)(x-1)/(x+1)³-(x-3)/(x+1)=(x-1)/(x+1)-(x-3)/(x+1)=(x-1-x+3

应该是x＋x分之1=3吧原式=(x平方＋1＋x平方分之1)分之1=[(x+1/x)平方-1]分之1=（3平方-1）分之1=8分之1

(x+y)/(x^4-y^4)÷1/(x^2+y^2)=(x+y)/(x^2+y^2)(x^2-y^2)÷1/(x^2+y^2)=(x+y)/(x^2-y^2)=(x+y)/(x+y)(x-y)=1/

x^2-3x+1=0x^2+1=3xx+1/x=3(x+1/x)^2=9x^2+1/x^2+2=9x^2+1/x^2=7(x^2+1/x^2)^2=49x^4+1/x^4+2=49x^4+1/x^4=

(x4+1)(x+1)(x-1)再问：过程再答：原式=x4(x2-1)+x2-1=(x4+1)(x2-1)=(x4+1)(x+1)(x-1)再问：已知：a-b=3,.a+c=-5,求ac-bc+a2-

x+1/x=3两边平方x^2+2*x*1/x+1/x^2=3^2x^2+2+1/x^2=9x^2+1/x^2=7x^2/(x^4+x^2+1)上下除以x^2=1/(x^2+1+1/x^2)=1/(7+

(x4+x2+1)/x2=x2+1+1/x2=(x+1/x)^2-2+1=9-1=8所以所求=1/8(x4=x^4,凑合看)

x平方-3x+1=0二边同除以xx-3+1/x=0x+1/x=3x^2+1/x^2=(x+1/x)^2-2=3^2-2=7x^4+1/x^4=(x^2+1/x^2)^2-2=7^2-2=47

x^2-4x+1=0两边除以xx+/x=4则x^2+1/x^2=14x^4+1/x^4+2=14^2则x^4+1/x^4=14^2-2