求学霸解其中两题。可以只回答一个!!
1.若x^2-3x-1=0,则x^2+1/x^2=_____;(x+1/x)^2=____;x^4+1/x^4;x^2/x^4+x^2+1=______
可答可不答:(x-2017)(2018-x)=-20,则(2017-x)^2+(x-2018)^2及(4035-2x)^2
急!请学霸帮忙!
基本就是这么算的
x^2-3x-1=0
两边同时除以x
x-3-1/x=0
x-1/x=3
两边平方
(x-1/x)^2=9
x^2-2+1/x^2=9
x^2+1/x^2=11
(x+1/x)^2=x^2+2+1/x^2=11+2=13
x^4+1/x^4=(x^2+1/x^2)-2=11^2-2=121-2=119
x^2/(x^4+x^2+1)
=1/[(x^4+x^2+1)/x^2]
=1/(x^2+1+1/x^2)
=1/(11+1)
=1/12
①解:x-3-1/x=0
x-1/x=3
(x-1/x)²=9
x²-2+1/x²=9
x²+1/x²=11
(x+1/x)²=x²+1/x²+2=11+2=13
x4次方+1/x4次方=(x²+1/x²)²-2=11²-2=119
最后一个你写的不是很明确
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