HELP ME 20 POINTS?!?!?!!?!?

[tex]5 \times1 \frac{12}{13} [/tex] me

Find the condition that the zeros of the polynomial f(x) = x^3+3px^2+3px+r may be in a.p.

Long division setup showing an incomplete calculation. 12 is in the divisor, 6839 is in the dividend, and 5 hundreds and 6 tens is written in the quotient. 6000 is subtracted from 6839 to give 839. an unknown value represented by a box is being subtracted from 839. what number should be placed in the box to complete the division calculation?