Find the dimension of the space P5? Please explain Find the dimension of the space P5 (enter the integer only without a decimal point or spaces). Solution P5 will have a dimension of 6. P5 is basically a 5th order polynomial, so it must contain [1,x,x2,x3,x4,x5]. SInce there are 6 elements in the set, thus the dimension of P5 will be 6..