3. The table shows the soil density of several soil samples at different depths. Depth (m) 1 5 6 8 10 12 14 21 23 24 28
Soil density ( )
1045 1063 1102 1140 1191 1232 1249 1254 1265 1268 1273
(a) Write the quadratic regression equation that models the data. Let x = depth below the surface and let y = soil density.
(b) Use the equation to estimate the soil density of a sample at a depth of 20 m. Show your work.