①1-根号3×cos30°+（1/2）^-3=

①
1-√3*cos30°+(1/2)^(-3)
=1-√3*√3/2+8
=1-3/2+8
=15/2
②
x^2*y-y
=(x^2-1)y
=(x+1)(x-1)y
③
k=xy=-3*2=-6