Question

which of the following is a polynomial with roots 3, 5, and -5i?
a)f(x)=x^3-3x^2+25x-75
b)f(x)=x^3-3x^3+15x-25
c)f(x)=x^3-15x^2+25x-75
d)f(x)=x^3-3x^3+15x-75

Answer 1

@Maddy1251

Answer 2

Do you know how to deal with imaginary numbers?

Answer 3

Not really

Answer 4

An imaginary number is a complex number that can be written as a real number multiplied by the imaginary unit i, [note 1] which is defined by its property i2 = −1. The square of an imaginary number bi is −b2. For example, 5i is an imaginary number, and its square is −25

Answer 5

Also, have you tried plugging in other numbers?

Answer 6

Unless my calculations are wrong, which I am double checking, 3 only satisfies A. So, so far that can be the only answer.

Answer 7

So you're saying A?

Answer 8

It's the only one that can yield 3. I am checking the other two numbers.

Answer 9

Okay, thank you.

Answer 10

Well I read it wrong.

Answer 11

It wants the roots of the function.

Answer 12

uh oh

Answer 13

No, not uh-oh. Still simple.

Answer 14

to you maybe!

Answer 15

To find the roots of a function, we must factor. (No wonder why nothing would equal 0 all the way around. (-: )

Answer 16

Oh its not bad, I promise you.

Answer 17

okay makes sense! I'm bad at factoring

Answer 18

Its not easy at first. Takes time. I am looking now.

Answer 19

I will have the answer in a flash (-:

Answer 20

I may have it.

Answer 21

alright, awesome!

Answer 22

I am leaning towards C because so far these are the groups I am finding
Group 1: (x-3) • (-25)
Group 2: (x-15) • (-x2)
Group one gives roots of x=3, and x=5i.

Answer 23

I am having trouble finding one that yields x=5

Answer 24

But I got 2 of 3 roots, so if I was you, thats the one I would try.

Answer 25

C?

Answer 26

That's the one that yields x=3 and x=5i, and it could possibly yield root x=5. I was having trouble with all of them finding x=5.

Answer 27

Hold on.

Answer 28

@Michele_Laino want to check to see if C is correct?

Answer 29

In the mean time, can you help really quickly with one I've been having trouble with? It's "which of the following represents the zeros of f(x)=x^3-2x^2-6x+12?"
answer choices are:
a) -2, -sqrt 6, -sqrt 6
b) 2, sqrt 6, -sqrt 6 (definitely not the answer. I chose this one last time and it was wrong)
c) 2, sqrt 6, -sqrt 6
d) -2, sqrt 6, sqrt 6

Answer 30

@Maddy1251 you there?