#### Thank you for registering.

One of our academic counsellors will contact you within 1 working day.

Click to Chat

1800-5470-145

+91 7353221155

CART 0

• 0
MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping

# If the eqn x4 - 4x3 +a x2 +bx +1 = 0 has four positive roots, then show that a=6 and b=-4.

12 years ago

since all roots are positive,

coeff. of x shld be negatuve i.e., b is negative

let roots be m(>0), n(>0), p(>0), q(>0)

m+n+p+q = 4

mn+np+pq+mp+mq+nq = a

mnp+mnq+npq+mpq = -b

mnpq = 1

For the objective case,

put m=n=p=q =1 (which satisfies eqns 1 and 4 above)

so a = 1+1+1+1+1+1 = 6

-b = 1+1+1+1 =4

so, a = 6 and b = -4

---

Please feel free to post as many doubts on our disucssion forum as you can. If you find any question difficult to understand - post it here and
we will get you the answer and detailed solution very quickly.We are all IITians and here to help you in your IIT JEE preparation. All the best.

Regards,
Naga Ramesh
IIT Kgp - 2005 batch