设切点为(t,t^2)y'=2x, y'(t)=2t切线为y=2t(x-t)+t^2=2tx-t^2代入B(2,3)到切线： 4t-t^2=3(t-1)(t-3)=0t=1, 3当t=1时，切线为y=2x-1当t=3时，切线为y=6x-9
