EXAMPLE 3 Express the definite integral
\int_3^7 (x^(2)-1)dx
as a limit of Riemann sums.
Solution We have
\int_3^7 (x^(2)-1)dx=\lim_(n->\infty )((x_(0)^(2)-1)+(x_(1)^(2)-1)+cdots+(x_(n-1)^(2)-1))w
where w=(4)/(n) and x_(0)=3,x_(1),x_(2),dots,x_(n)=7 all divide the interval 3,7 up into n
even subintervals, all of width w.