5(3a²b-ab²)-(ab²+3a²b)
=15a²b-5ab²-ab²-3a²b
=(15a²b-3a²b)-6ab²
=12a²b-6ab²
=6ab(2a-b)
若a=1/2 b=1/3
6ab(2a-b)
=6*1/2*1/3(2*1/2-1/3)
=1-1/3
=2/3
5(3a²b-ab²)-(ab²+3a²b)
=15a²b-5ab²-ab²-3a²b
=(15a²b-3a²b)-6ab²
=12a²b-6ab²
=6ab(2a-b)
若a=1/2 b=1/3
6ab(2a-b)
=6*1/2*1/3(2*1/2-1/3)
=1-1/3
=2/3