If P(x)=x3+ax2+bx+cP(x) = x^3 + ax^2 + bx + cP(x)=x3+ax2+bx+c has roots in arithmetic progression, what is a necessary condition?
2a3−9ab+27c=02a^3 - 9ab + 27c = 02a3−9ab+27c=0
a3−9ab+27c=0a^3 - 9ab + 27c = 0a3−9ab+27c=0
2a3−9ab+9c=02a^3 - 9ab + 9c = 02a3−9ab+9c=0
a3+9ab+27c=0a^3 + 9ab + 27c = 0a3+9ab+27c=0