Beartou.com 尝试计算一: (1)(x+2y)(5a+3b) 拆分成多个单项式:(x,2y)(5a,3b) 3 按法则算得:x5a,x3b,2y5a,2y3b 3 积相加得:x·5aX3b+2y·5a2y3b 解:(x+2y)(5a+36) =X·5a+X3b+2y5a+2y3b 5ax +30X +10ay +6by
尝试计算一： (1) (x+2y)(5a+3b) ; 拆分成多个单项式：（x，2y）（5a，3b） 按法则算得：x·5a , x·3b , 2y·5a , 2y·3b 积相加得：x·5a+x·3b+2y·5a+2y·3b 解：(x+2y)(5a+3b) =x ·5a +x ·3b +2y ·5a +2y ·3b =5ax +3bx +10ay +6by 4 1 2 3 1 2 3 4
己会?em (2)(2X-3)(X+4) 拆分成多个单项式:(2x,-3)(x,4) 按法则算得:2XX,2X·4,-3X,-34 积相加得:2xX2x4(-3)X+(-3)4 解:(2X-3)(X+4)=2x2+8x-3X-12 =2x2+5X-12
(2) (2x–3)(x+4) ; 拆分成多个单项式：（2x，-3）（x，4） 按法则算得：2x·x, 2x·4, -3·x , -3·4 积相加得：2x·x+2x·4+(-3)·x+(-3)·4 解：(2x–3)(x+4) 2x2+8x –3x –12 =2x2 +5x = –12 1 2 3 4 1 2 3 4