kill(all)$

van=facebook.com/LearningCalculus;

a(t):=(2*t+3)^2-1;

b(t):=2*(2*t+3);

c(t):=(2*t+3)^2+1;

pythag(t) := a(t)^2+b(t)^2=c(t)^2$

pythag(t);

expand(pythag(t));

factor(pythag(t));