求代数式的值x+1/x=3,求x^2
x+1/x=3,求x^2-1/x^2=?
x+1/x=3 x^2+1/x^2+2=9 x^2+1/x^2-2=5 (x-1/x)^2=5 x-1/x=±√5 x^2-1/x^2=(x+1/x)(x-1/x)=±3√5