1.已知X^2+1/X^2=3,求X+1/x的值2.若|2A-5|与根号B+2互为相反数,求AB的值

题目

1.已知X^2+1/X^2=3,求X+1/x的值2.若|2A-5|与根号B+2互为相反数,求AB的值

答案

设z^2=(x+1/x)^2=X^2+1/X^2+2=3+2=5
X+1/x=z=+根号5or-根号5
|2A-5|+根号B+2=0
所以2A-5=0 A=5/2
B+2=0 B=-2