need help with 1 more algebra problem

[coder1]

Ok, I have no idea where to begin on this one?

Determine the value of k such that kx^3-x^2-5kx+12 is divisible by x-2

Am I suppose to use synthetic division? Thanks for any help.

 

[Rkonster]

If it is divisible, then the remainder is 0. Divide and solve for k.

 

[coder1]

Can you point me in the right direction? is k suppose to be the constant. thats what is throwing me off

 

[Rkonster]

Just pretend k is a number and divide like you normally would.

 

[coder1]

So I could set k as any value and the results would be the same?

 

[HardcoreRobot]

Originally posted by: coder1
So I could set k as any value and the results would be the same?

The idea is to find a value of k that satisfies the situation, so arbitrarily picking one is not a good way to do it 🙂

 

[sash1]

use synthetic division. You know the remainder has to be 0. I got k=4

`K

 

[Muzzan]

While you could use polynomial division, there is an easier way... If f(x) = kx^3 - x^2 - 5kx + 12 is divisible by (x - 2), then x = 2 is a root of f(x). Thus f(2) = 0. Should be pretty easy from there on...

 

[GreatBarracuda]

Originally posted by: coder1
So I could set k as any value and the results would be the same?

Ok. Since you know that x-2 is a factor of the expression, substituing x = 2 in the expression would make it equal to zero. So doing that will give you:

8k - 4 - 10k + 12 = 0
2k = 8
k = 4

Voila!

 

[eLiu]

Originally posted by: GreatBarracuda

Originally posted by: coder1
So I could set k as any value and the results would be the same?

Ok. Since you know that x-2 is a factor of the expression, substituing x = 2 in the expression would make it equal to zero. So doing that will give you:

8k - 4 - 10k + 12 = 0
2k = 8
k = 4

Voila!

Ding ding ding! I was about to say...no need for synthetic division here, good lord.

 

[halik]

algebra.... thats one of those things you forget after surface and vector integrals. All of my friends agree that after taking years of calc, you have no idea how to do stuff like that

 

[cchen]

Originally posted by: halik
algebra.... thats one of those things you forget after surface and vector integrals. All of my friends agree that after taking years of calc, you have no idea how to do stuff like that

actually, its pretty sad if you've taken calc and can't figure that one out

 

[cronos]

Originally posted by: cchen

Originally posted by: halik
algebra.... thats one of those things you forget after surface and vector integrals. All of my friends agree that after taking years of calc, you have no idea how to do stuff like that

actually, its pretty sad if you've taken calc and can't figure that one out

yes. you should be able to do that in your head.

 

[GreatBarracuda]

Originally posted by: saxguy

Originally posted by: cchen

Originally posted by: halik
algebra.... thats one of those things you forget after surface and vector integrals. All of my friends agree that after taking years of calc, you have no idea how to do stuff like that

actually, its pretty sad if you've taken calc and can't figure that one out

yes. you should be able to do that in your head.

Sometimes it's the way the question is set up. I don't think he meant Algebra in general, because that's sad 🙂

 

[naruto1988]

oh god, it's summer. i'm trying to stay away from algebra, lol. why did i click into this thread? hrm...

 

[User1001]

Originally posted by: GreatBarracuda

Originally posted by: saxguy

Originally posted by: cchen

Originally posted by: halik
algebra.... thats one of those things you forget after surface and vector integrals. All of my friends agree that after taking years of calc, you have no idea how to do stuff like that

actually, its pretty sad if you've taken calc and can't figure that one out

yes. you should be able to do that in your head.

Sometimes it's the way the question is set up. I don't think he meant Algebra in general, because that's sad 🙂

It's not algebra problems that most of us forget in calc, it's the geometry. At least thats how it is with my friends.

 

[EngenZerO]

this makes me so glad that I dont have to take any more math classes evar... evar!!!