2道代数题!1.已知：x+1/x=3,求x^2/(x^4+x^2+1)的值.2.化简：√（7+4√3）+√(7-4√3)

2道代数题!1.已知：x+1/x=3,求x^2/(x^4+x^2+1)的值.2.化简：√（7+4√3）+√(7-4√3)
2道代数题!
1.已知：x+1/x=3,求x^2/(x^4+x^2+1)的值.
2.化简：√（7+4√3）+√(7-4√3)

2道代数题!1.已知：x+1/x=3,求x^2/(x^4+x^2+1)的值.2.化简：√（7+4√3）+√(7-4√3)
1.
x+1/x=3,则x^2+1/x^2=(x+1/x)^2-2=7
x^2/(x^4+x^2+1)上下同除以x^2,
得1/(x^2+1/x^2+1)=1/(7+1)=1/8
2.
7+4√3=(2+√3)^2,
7-4√3=(2-√3)^2,
所以原式=2+√3+2-√3=4