(1).(a^2+3)(a-2)-a(a^2-2a-2)
=a^3-2a^2+3a-6-a^3+2a^2+2a
=5a-6
(2).(2×10^3)·(8×10^6)
=2*8*10^9
=1.6*10^10
(3).(2x+1)(x-3)
=2x^2-6x+x-3
=2x^2-5x-3
(4).2a^2b·(-1/2a^2b^3+5ab^2)-3a^2b·(-2/3ab)·5ab^2
=-a^4b^4+10a^3b^3+10a^4b^4
=10a^3b^3+10a^4b^4
(5).(2a+3)(3/2b+5)
=3ab+10a+9/2b+15