It looks like they've done the multiplication for you and added in the correct +/- signs). Just copy the numbers in the row above into the blanks
example, First two rows
16a^5 + 4a^3 - 4a^2 + 3a - 1
16a^5 + 4a^3 + 0 + 0 + 0 - 8a^4
-16a^5 - 4a^3 + 0 + 0 + 0 + 8a^4
---------------------------------------------------
8a^4 - 4a^2 + 3a - 1
