group together the values with same co-effiecients; like (q+p)x^3 etc etc.
equate the co-effiecients on the left hand side to the now grouped ones on the right, for example [x^3]: -2x^3= (q+p)x^3, the x^3 cancels and ull get an equation only in terms of p and q. do the same for [x] and ull get an equation with only q, solve this and get the value for q [q = 2].
sub in this value for the [x^3] equation and ull get an answer for p [p= -4].
