A box has 4 white and 3 red balls. Two balls are taken out in succession. What is the probability that both are white?

£^-1F(s) = f(t)

£[a f₁(t) + bf₂(t)] = aF₁(s) + bF₂(s)

where

£[f(t - T)] = e^-sT F(s)

£[e^-at f(t)] = F(s + a)

Initial value theorem

Final value theroem

Convolution Integral

where t is dummy variable for t.

Include unity circle and exterior of circle hence x(z) will be stable, causal.