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# C3 Remainder Theorem and equating co-efficients. watch

1. C3 Heinemann Modular, page 8 [Example 12]

So i can work out C and D, but i can't figure out how 1 = A and then B = 4

They're saying to compare co-efficients but i don't understand. help please.
Can't move on till i work this out..
I haven't written out the question because i don't know how to use Latex or whatever it's called, sorry.

Rei.
2. Well given hardly any of us are going to have the book to hand I suggest you do your best to reproduce the question.
3. (Original post by Rei)
C3 Heinemann Modular, page 8 [Example 12]

So i can work out C and D, but i can't figure out how 1 = A and then B = 4

They're saying to compare co-efficients but i don't understand. help please.
Can't move on till i work this out..
I haven't written out the question because i don't know how to use Latex or whatever it's called, sorry.

Rei.
There's a link above your post called "How to use LaTeX". Have a look at it! The equation can't be that bad that it'll take you ages to figure out how to post it in Latex.
4. take a picture or scan it
5. I don't have the question.

But, if you're dividing something by one of its factors, the remainder must equal 0. So if you're remainder is something like , then what you do is say , and then you equate like with like. So and so on.

Do you understand?

And if you know that x - 3 is a factor and hence f(3) = 0 or whatever then it's the same dealy. x terms = x terms, x^2 terms = x^2 terms and such.

I dunno what the question is asking or anything but yeah.
6. When you open up the bracket, you have to look at the matching variables:

So when we look at the co-efficient (The numbers in front of ), we get

Similarly,

So when we look at the co-efficient (The numbers in front of ), we get but since we know what is then we can substitute its value to get .
7. Sorry, i didn't make this clear enough.. i understand what a co-efficient is. I just don't understand how the were able to equate to when in the question it's

Same with B and the
8. (Original post by Rei)
Sorry, i didn't make this clear enough.. i understand what a co-efficient is. I just don't understand how the were able to equate x^3 to Ax^3 when in the question it's Ax^2.

Same with B and the x^2.
It's not Ax^2. It's (Ax^2 + stuff)(x + stuff), which multiplies out to give you Ax^3. (If I read the question correctly.)
9. (Original post by generalebriety)
It's not Ax^2. It's (Ax^2 + stuff)(x + stuff), which multiplies out to give you Ax^3. (If I read the question correctly.)
So, you multiply by for A, then simply compare those co-efficients. What about for B, you multiply by -3? if so, how comes.. ?
10. (Original post by Rei)
So, you multiply by for A, then simply compare those co-efficients. What about for B, you multiply by -3? if so, how comes.. ?
Ho hum.

Multiply out the brackets on the RHS, it'll make the whole thing a lot clearer to you. All they're doing is multiplying the brackets out systematically in their heads.
11. (Original post by generalebriety)
Ho hum.

Multiply out the brackets on the RHS, it'll make the whole thing a lot clearer to you. All they're doing is multiplying the brackets out systematically in their heads.
LOL, I just looked at it again.. figured out what the hell was wrong with me.. Ahhhh for some stupid reason i kept working the expansion out mentally and coming to -2Ax^3 when i multiplied by -3. Thanks for that.

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