若x^?+x^-?=9,则x^2+1/x^2=?若x^?-x^-?=3,则x^2+1/x^2=?我打错了，应是若x^1/2+x^-_数学解答

若x^?+x^-?=9,则x^2+1/x^2=?若x^?-x^-?=3,则x^2+1/x^2=?
我打错了，应是若x^1/2+x^-1/2=9,则x^2+1/x^2=?
若x^1/2-x^-1/2=3,则x^2+1/x^2=?

人气：129 ℃　时间：2020-09-14 01:02:31

解答

这就看你对问题的把握了,应定要仔细观察题目已知与未知的联系.本题中已知为一次,未知为二次,正好通过平方求得,x^(1/2)+x^(-1/2)=9x^2+1/x^2=(x+1/x)^2-2=[(x^(1/2)+x^(-1/2)^2-2]^2-2=(81-2)^2-2=6会了第一个,第二个...