脫式計算,注意使用簡便方法. ① -( + ) | ② - + | ③ +( - ) |
④ + + | ⑤ + + + | ⑥ + + + . |
解:①

-(

+

),
=

-

,
=0;
②

-

+

,
=

-

+

,
=

;
③

+(

-

),
=

+

,
=

;
④

+

+

,
=(

+

)+

,
=1+

,
=1

;
⑤

+

+

+

,
=(

+

)+(

+

),
=

+1,
=1

;
⑥

+

+

+

,
=(

+

)+(

+

),
=2+

,
=2

.
分析:①先算括號內(nèi)的,再算括號外的;
②通分計算;
③先算括號內(nèi)的,再算括號外的,同時注意通分;
④⑤⑥運用加法交換律與結(jié)合律簡算.
點評:考查了分?jǐn)?shù)的四則混合運算,注意運算順序和運算法則,靈活運用所學(xué)的運算定律簡便計算.
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