a)f (x)=x/2-5

y=x/2-5

y+5=x/2 

x=2(y+5) trocando x por y

y=2(x+5)

b)f(x)=3x2²+4

y=3x²+4

y-4=3x²

x²=(y-4)/3

x=V(y-4)/3 trocando

y=V(x-4)/3      

c)f(x)=6x-1/3x+2

y=19/3x+2

y-2=19/3x

19x=3(y-2)

x=(3/19)(y-2) trocando

y=(3/19)(x-2)