Use Descartes' Rule of Signs to find the number of possible positive real roots and the number of possible negative real roots for the function f(x) = x4 + 2x3 - 3x2 - 8x - 4.a.positive 1; negative 3 or 1c.positive 3; negative 3 or 1b.positive 1; negative 3 or 5d.positive 3; negative 3 or 5