解:(1)3x-
=
,
3x-
+
=
+
,
3x=
,
3x÷3=
÷3,
x=
;
(2)x+
x=42,
x=42,
x×
=42×
,
x=36;
(3)x-
x=32,
x=32,
x×
=32×
,
x=40;
(4)
+
x=
,
+
x-
=
-
,
x=
,
x×4=
×4,
x=
.
分析:(1)根據(jù)等式的性質(zhì),兩邊同加上
,再同除以3即可;
(2)原式變?yōu)?img class='latex' src='http://thumb.1010pic.com/pic5/latex/7580.png' />x=42,根據(jù)等式的性質(zhì),兩邊同乘
即可;
(3)原式變?yōu)?img class='latex' src='http://thumb.1010pic.com/pic5/latex/602.png' />x=32,根據(jù)等式的性質(zhì),兩邊同乘
即可;
(4)根據(jù)等式的性質(zhì),兩邊同減去
,再同乘4即可.
點(diǎn)評:在解方程時應(yīng)根據(jù)等式的性質(zhì),即等式兩邊同加上、同減去、同乘上或同除以某一個數(shù)(0除外),等式的兩邊仍相等,同時注意“=”上下要對齊.