The A.M of all the solutions of 4cos3x−4cos2x−cos(π+x)+1=0  in  (0,315)  is

4cos3x−4cos2x−cos(x+π)−1=0 4cos3x−4cos2x+cosx−1=0 4cos2xcosx-1+1cosx−1=0 cosx=1   has solutions as x=2π,4π,8π,....100π  in  (0,315)  ∴  A.M=sum of numbersno. of numbers=2π+4π+......+100π50=51π