课前预习答案
1、(1)不变;b<a
(2)a×(b×c)
(3)a×b+a×c
2、负;正
课堂探究例1思路导引答案
1、交换;结合
2、分配;分配
解:(1) -0. 125×(-25)×8×(-4)
=-0.125×8×(-25)×(-4)
=(-0.125×8)×[(-25)×(-4)]
=-1×100
= -100
(2)307× +393×()
=-307× -393×
= ×(-307-393)
=36/7×(-700)
=-3600
(3)[(+1/5)+(-1/2)+(-5/12)]×(+60)
=1/5×60+(-1/2)×60+(-5/12)×60
=12-30-25=-43
课堂探究例1变式训练1-1答案
A
课堂探究例1变式训练1-2答案
解:(1)原式=[-8×(-6)]×[5×(-0.4)]
=48×(-2) =-96
(2)原式=[(-12/5)×5/18]×[(-9/4)×(-2/3)]
=-2/3×3/2
=-1
(3)原式=1/2×(-36)-5/9×(-36)+5/6×(-36)
=-18+20-30
=-28
(4)原式=17.4×[(-2/3)+(-1/3)]
=17.4×(-1)
=-17.4
课堂探究例2思路导引答案
1、3;负;2;正
2、0
解:(1)原式=-(10×1/4×1/10)=-1/4
(2)原式=3×5/6×9/5×1/4=9/8
(3)原式=0
课堂探究例2变式训练2-1答案
D