options ls=75 formdlim="-";
data one;
   input y   x1  x2;
   x1x2=x1*x2;
cards;
1.7 4.2 6.9
1.9 3.6 2.3
2.1 4.7 7.6
2.8 5.2 5.8
2.2 4.6 8.1
2.9 5.0 8.6
3.4 5.4 1.7
4.1 7.0 6.9

run;
proc reg;
   model y=x1 x2/p;
   model y=x1 x2 x1x2;
run;