2x^2+6x-3=0的两个根为X1和X2
∴x1+x2=-3,x1·x2=-3/2
(x1-x2)²
=(x1+x2)²-4x1·x2
=9+3/2×4
=15
(x1+3)(x2+3)
=x1·x2+3(x1+x2)+9
=-3/2-9+9
=-3/2