若x^2+3x+1=0,试求的x^2+1/X^2值

Question

若x^2+3x+1=0,试求的x^2+1/X^2值

Answer 1

由x^2+3x+1=0两边同时除以X得:
x+3+1/x=0
即x+1/x=-3
再由 x+1/x=-3两边同时平方得:
x^2+2+1/x^2=9
所以x^2+1/X^2=7