解方程: (1)215x x -+= (2)1
4342
x x -=+
(3)23
41255x x -=+ (4)2 3.5 4.51x x -=-
(5)76226x x --=-; (6)4352x x --=--;
(7)453x x =+; (8)3735y y +=--
(1)2(x-1)+4=0 (2)4-(3-x)=-2
(3)(x+1)-2(x-1)=1-3x (4)2(x-2)-6(x-1)=3(1-x)
(5)4(x-1)-10(1-2x)=-3(2x+1) ( 6) 2(x+3)-5(1-x )=3(x-1)
(7) 3(x+1)-2(x+2)=2x+3 (8)2(x-1)-(x-3)= 2(1.5x-2.5)
(9)3(x-7)-2[9-4(2-x)]=22 (10)3x-2[3(x-1)-2(x+2)]=3(18-x)
(11)
x x 3221221413223=-??
?
???+??? ??+ (12) x x 23231423 =??????-??? ??-
(1)
2x =3x-1 15
12 (2)=-+x x
12136x x x -+-
=- 12
136
x x x -+-=-
(5)
124362x x x -+--=
(6)112
[(1)](1)223
x x x --=- (7)
35.012.02=+--x x (8)x x -=+3
8
(9)43(1)323322x x ??---=????
(10)2x -13 =x+22 +1
(11)3142
1
25
x x
-+
=-(12) 31257
2
43
y y
+-
=-
一架飞机飞行在两个城市之间,顺风需2小时,逆风需3小时,已知风速为20千米/时,求两个城市之间的距离