Can someone help me with this, I don't really understand how to do it, if you help me with one step by step i could figure out the rest.

For each real function described , give all the values of v for which the function has singularities and tell whether the singularities are removable. If the singularities are removable, redefine the function to make it continuous.

a)f(x)=tanx

b)g(t)=((t^2)-t)/(t-1)

c)h(a)=a/((3a^2)-2a-8)

d)j(y)=(y-1)(y+2)(y-3)