Question

If x^4+ax^3+bx^2+cx+d=0 has four positive real roots then
A) ac+16d>=0
B) ac-16d<=0
C) b^2-36d<=0
D) b^2+36d>=0

Urgent plse asap

Answer 1

If you expand (x-m)(x-n)(x-p)(x-q) you get a set of positive k values
x^4 - k1 x^3 + k2 x^2 - k3 x + k4
That means that ac > 0 and of course, d > 0
So, A is looking good.
A little experimentation will show that the others are not always true.