(1)a的3倍的相反数可表示为_-3a__,系数为__-3___,次数为__1___.
(2)2a^2-[0.5(ab-a^2)+8ab]-0.5ab
=2a^2-0.5ab+0.5a^2-8ab-0.5ab
=2.5a^2-9ab
(3)7x^2-5x+3-2x+3x^2-5
=10x^2-7x-2
(4)-2(xy-3y^2)-[2y^2-5(xy+x^2)+2xy]
=-2xy+6y^2-2y^2+5xy+5x^2-2xy
=xy+4y^2+5x^2