×4+3×1×3×12××(21+1-2)73×72×(-)×35×67+13×++++
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解:(1)×4+,
=×(4+1),
=×5,
=2;
(2)3×1×3×,
=×××,
=××,
=10×,
=2;
(3)12×,
=12×(1-),
=12×1-12×,
=12-,
=11;
(4)×(21+1-2),
=×21+×-×,
=15+1-2,
=16-2,
=14;
(5)73×,
=(72+)×,
=72×+×,
=45+,
=45;
(6)72×(-)×35,
=(72×35)×(-),
=(72××35)-(35××72),
=(64×35)-(5×72),
=2240-360,
=1880;
(7)×67+13×,
=×13+13×,
=(+)×13,
=4×13,
=52;
(8)++++,
=(-)+(-)+(-)+(-)+(-),
=-+-+-+-+-,
=-,
=.
解析分析:(1)运用乘法分配律简算;
(2)(4)按照从左到右的顺序计算;
(3)先把化简成1-,再运用乘法分配律简算;
(5)先把73化简成72+,再运用乘法分配律简算;
(6)先把72×35结合在一起,再运用乘法分配律简算;
(7)先根据积不变规律,把×67变成×13,再运用乘法分配律简算;
(8)=-,=-…由此化简求解.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.