If the equation has four distinct real roots

MATHEMATICS · Single correct · AP · Calculus AB · Analytical Applications of Differentiation · Analytical Applications of Differentiation

Problem

If the equation

x^4+8x^3+18x^2+8x+a=0

has four distinct real roots, then the range of

a

is (a)

(0,9)

(b)

(-9,0)

(c)

(-8,1)

(d)

(-1,8)