If roots of the equation ax3+bx2+cx+d=0 remain unchanged by increasing each coefficient by one unit, then
a = b = c = d ≠ 0
a≠0, b+c=0, d≠0
a≠b≠c≠d≠0
a = b ≠ c = d ≠ 0
The roots of ax3+bx2+cx+d=0 and (a+1)x3+(b+1)x3+(c+1)x+(d+1)=0 are same. ∴ a+1a=b+1b=c+1c=d+1d ⇒ a=b=c=d≠0