Okay, so I know you have to rationalize the limit in order to get it out of the indeterminate form, but I can't seem to do it for these two questions. Can someone help, start me off?

a) Lim as x -> 4 of (x^2-4)/(sqrtx - 2)

b) Lim as x -> 0 of [sqrt(3-x) - sqrt(x+3)] / x

Thanks,

Stefan