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

Total Price: Rs.

There are no items in this cart.
Continue Shopping
Tushar Watts Grade: 12

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

8 years ago

Answers : (1)

Ramesh V
70 Points

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.


Naga Ramesh

IIT Kgp - 2005 batch




8 years ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies
  • Complete JEE Main/Advanced Course and Test Series
  • OFFERED PRICE: Rs. 15,900
  • View Details

Ask Experts

Have any Question? Ask Experts

Post Question

Answer ‘n’ Earn
Attractive Gift
To Win!!! Click Here for details