解:3a-2a-5a+2b等于( -4a + 2b ) ∵已知需求出3a-2a-5a+2b等于多少 A + 2A = (1+ 2)= 3A ∴3a - 2a - 5a + 2b = a - 5a + 2b = -(5a - a)+ 2b = - 4a + 2b 答:3a-2a-5a+2b等于- 4a + 2b
=a(3-2-5)+2 b=2b-4a
原式=(3-2-5)a+2b=-4a+2b