1.2/b+2=4/b
2+2b=4
2b=4-2
2b=2
b=1
2.5y+7/4=5y/3
60y+21=20y
60y-20y=-21
40y=-21
y=40/-21
y=-1,1
3.4/2c+6=10/7c-2
28+84c=20-28c
84c+28c=20-28
112c=-8
c=14
4.2a-4/a²+2a=3/a
2a³-4+2a³=3a
2a³-4+2a³-3a=0
2a(a²+a²-4-3)=0
2a=0 или 2a²-7=0
a=0 2a²=7
a²=7/2
a1=3,5 a2= -3,5