Someone i know how to find the quotient but i don't know if i have to put an addition sign in the middle of each term or subtraction sign?

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

The last answer choice