Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

## #1 2012-10-19 04:03:33

danthemaths
Novice

Offline

### The Remainder Theorem

hey guys, I am stuck on this question:
"The Remainder when x^3-2x^2+ax+5 is divided by x-3 is twice the remainder when the same expression is divided by x+1. Find the value of the constant a."
I know the answer is 4 but i dont know how to get there.

I have started it off but dont know what to from then on...

I worked out f(3) to be -14=3a
...and f(-1) to be a=2

Am I on the right lines? and what do I do from then on? this will really help me out

danthemaths

## #2 2012-10-19 04:55:39

bob bundy
Moderator

Offline

### Re: The Remainder Theorem

hi danthemaths

Welcome to the forum.

Am I on the right lines?

Not quite.

When you put x = 3 you get a remainder.  Let's say

and when x =-1

You are also told that

So make an equation from this and solve for a.

Hope that helps.

?? But I'm not getting a = 4  ??

Bob

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei