原式=4a-2b-(9b-6a)+10b-5a=8b-a-9b+6a=5a-b

原式=(2/3)a²-[(2/3)a³-2a²+(4/3)ab-(1/6)a²b+(1/2)ab-(1/3)b²]

=(2/3)a²-(2/3)a³+2a²-(11/6)ab+(1/6)a²b+(1/3)b²

=(8/3)a²-(2/3)a³-(11/6)ab+(1/6)a²b+(1/3)b²