解:(1)
×
+
÷
,
=
×
+
×
,
=(
+
)×
,
=1×
,
=
;
(2)
-(2-
-
),
=
-[2-(
+
)],
=
-[2-1],
=
-1,
=
;
(3)12×(
-
),
=12×
-12×
,
=10-9,
=1;
(4)
+
÷
+
,
=
+
×
+
,
=
+
+
,
=
+(
+
),
=
+1,
=1
;
(5)(
)×(
÷
),
=
×(
×
),
=
×2,
=
;
(6)[
-(
+
)]÷4,
=[
-
-
)]÷4,
=[
-
]÷4,
=
×
,
=
.
分析:(1)把除法改為乘法,運(yùn)用乘法分配律的逆運(yùn)算簡(jiǎn)算;
(2)括號(hào)內(nèi)運(yùn)用減法的性質(zhì)簡(jiǎn)算,算出結(jié)果后,再算括號(hào)外的減法;
(3)運(yùn)用乘法分配律簡(jiǎn)算;
(4)先計(jì)算
÷
=
,再運(yùn)用加法結(jié)合律簡(jiǎn)算;
(5)按運(yùn)算順序計(jì)算,兩個(gè)括號(hào)同時(shí)計(jì)算;
(6)運(yùn)用減法的性質(zhì)先去小括號(hào),運(yùn)用結(jié)合律計(jì)算
-
,因?yàn)槔ㄌ?hào)內(nèi)有
,為了便于計(jì)算,把
-
的結(jié)果寫(xiě)成
,最后算中括號(hào)外的除法.
點(diǎn)評(píng):此題主要考查分?jǐn)?shù)的四則混合運(yùn)算的運(yùn)算順序和應(yīng)用運(yùn)算定律進(jìn)行簡(jiǎn)便計(jì)算.