Corrected the Extrapolated function in both Dense and Sparse of Regression. And added test code to tests/Explanatory

Signed-off-by: Timothy Humphrey <timothy.humphrey@lexisnexis.com>
Corrected the Extrapolated function in both Dense and Sparse of Regression. And added test code to tests/Explanatory

Signed-off-by: Timothy Humphrey <timothy.humphrey@lexisnexis.com>