Polynomial

Let P(x) = x^{6}-x^{5}-x^{3}-x^{2}-x

Q(x) = x^{4}-x^{3}-x^{2}-1

If
a,b,c,d are roots of q(x) then find the value of P(a)+P(b)+P(d) ?

11 Answers

21
Arnab Kundu ·

Please, do you mean p a + pb +pc + pd

71
Vivek @ Born this Way ·

No, It is what's it's given.

21
Arnab Kundu ·

How are u sure?

71
Vivek @ Born this Way ·

I believe it is so..

11
Sambit Senapati ·

Do, we have to find the answer in terms of a, b, c, d. I'm getting a long expression with the help of brute force.

1
rishabh ·

arnab is right, it should be P(a)+P(b)+P(c)+P(d)
P(x) = Q(x)(x2+1)+x2-x+1
=> ΣP(a) = Σa2-a+1
=> which can be easily found by using vieta's
=> im getting the answer as 6

71
Vivek @ Born this Way ·

@Risabh.. It is okay for what it isn't asked.

Anyways, I seem to get 3 as answer, But I don't know the correct answer, so may be you people help.

1
rishabh ·

you are getting 3 as an answer for the question you typed?

71
Vivek @ Born this Way ·

Yes!

21
Shubhodip ·

Can you post how you did it? It'll help us to help you !

71
Vivek @ Born this Way ·

I just assumed that one obvious root of q(x) i.e., -1 is equal to c. I thought so because it is not given that which are complex or which are real, and order also doesn't matters. So it can well be assumed?

This will easily yield the answer 3.

This was an integer type question. So it think they might have tricked us into something like this

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