The table gives the values of a function obtained from an experiment. Use them to estimate

9
f(x) dx
3
using three equal subintervals with right endpoints, left endpoints, and midpoints.
x 3 4 5 6 7 8 9
f(x) −3.5 −2.1 −0.5 0.2 0.8 1.3 1.8

(c) Estimate
9
f(x) dx
3
using three equal subintervals with midpoints.
M3 =?