当a=-1,b=-2时,代数式7a2b-(-4a2b+5ab2)-2(2a2b-3ab2)的值

7a2b-(-4a2b+5ab2)-2(2a2b-3ab2)
=7a²b+4a²b-5ab²-4a²b+6ab²
=7a²b+ab²
当a=-1,b=-2时
原式=7a²b+ab²=-14-4=-18

7a^2b-(-4a^2b+5ab^2)-2(2a^2b-3ab^2)
=7a^2b+4a^2b-5ab^2-4a^2b+6ab^2
=7a^2b+ab^2
=ab(7a+b)
=(-1)x(-2)x[7x(-1)+(-2)]
=2x(-7-2)
= -18