Using binomial theorem for the expansion of (2x−3)6, we have
(2x−3)6=6C0(2x)6+6C1(2x)5(−3)+6C2(2x)4(−3)2+6C3(2x)3(−3)3+6C4(2x)2(−3)4+6C52x5(−3)2+6C6(−3)6
=64x6+6.32x5(−3)+15.16x4.9+20.8x3(−27)+15.4x2.81+6.2x(−243)+729
=64x6−576x5+2160x4−4320x3+4860x2−2916x+729