用简便方法计算:
①;
②;
③;
④-989×(-9)+989×(-19)-(-989)×10.
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解:①
=-1+×24+×24-×24-×24
=-1+12+16-18-22
=-13;
②
=(-100+)×198
=-100×198+×198
=-19800+2
=-19798;
③
=+6.125+
=8;
④-989×(-9)+989×(-19)-(-989)×10
=989×(9-19+10)
=989×0
=0.
解析分析:根据乘法分配律简便计算即可求解.
点评:考查了有理数的乘法,注意灵活运用运算律简便计算.