问题
解答题
| 用简便方法计算： ①(-32
②-99
③(-3)×(-
④-989×（-9）+989×（-19）-（-989）×10． |
答案
①(-32
)×16 25
-(1 32
+1 2
-2 3
-3 4
)×(-24)11 12
=-1
+1 50
×24+1 2
×24-2 3
×24-3 4
×2411 12
=-1
+12+16-18-221 50
=-13
；1 50
②-99
×19898 99
=（-100+
）×1981 99
=-100×198+
×1981 99
=-19800+2
=-19798；
③(-3)×(-
)+0.25×24.5+(-51 4
)×(-25%)1 2
=
+6.125+3 4 11 8
=8
；1 4
④-989×（-9）+989×（-19）-（-989）×10
=989×（9-19+10）
=989×0
=0．