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'Factorising with Multilink' printed from http://nrich.maths.org/

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For this problem, you will either need multilink cubes or these sets of number base sheets to cut out: Base Three Base Four Base Five Base Six.

 

In the video below, Charlie and Alison show how you can make rectangles using sets of squares, sticks and units.
 


Can you make a rectangle to represent $x^2 + 7x + 12$?
Can you do it in more than one base?

Watch the video below to see how Charlie and Alison tackled this question:
 



Take 1 square and 12 units in your chosen base. Put them together with some sticks to make rectangles that will work in all bases.

Charlie and Alison made $x^2 + 7x + 12$ into a rectangle with length $x+4$ and width $x+3$.

How many different rectangles can you make?
What do you notice about the dimensions of your rectangles?

Imagine you had 1 square, lots of sticks and 100 units. What can you say about the dimensions of the rectangles it is possible to make?


Now, take 1 square and 12 sticks in your chosen base. Put them together with some units to make rectangles that will work in all bases.

How many different rectangles can you make?
What do you notice about the dimensions of your rectangles?

Imagine you had 1 square, 100 sticks and lots of units. What can you say about the dimensions of the rectangles it is possible to make?

 

If you had 1 square, $p$ sticks and $q$ units, what can you say about the dimensions of the rectangles it is possible to make?

 

Extension

Think about the rectangles it's possible to make if you use two, three, four... squares, some sticks and some units.

 

Many thanks to Paul Andrews whose ideas inspired this problem.