1.若x+y=3,x-y=负2,则x的平方减y的平方等于

x^2-y^2=(x+y)(x-y)=-6
(m-1/m)^2=m^2-2+1/m^2=16
m^2+1/m^2=18
(m^2+1/m^2)^2=m^4+2+1/m^4=324
m^4+1/m^4=322