There are **24** NRICH Mathematical resources connected to **Expanding and factorising quadratics**, you may find related items under Algebraic expressions, equations and formulae.

The sums of the squares of three related numbers is also a perfect square - can you explain why?

Choose four consecutive whole numbers. Multiply the first and last numbers together. Multiply the middle pair together. What do you notice?

Show that if you add 1 to the product of four consecutive numbers the answer is ALWAYS a perfect square.

Can you convince me of each of the following: If a square number is multiplied by a square number the product is ALWAYS a square number...

Take a triangular number, multiply it by 8 and add 1. What is special about your answer? Can you prove it?

Take any prime number greater than 3 , square it and subtract one. Working on the building blocks will help you to explain what is special about your results.

Many numbers can be expressed as the difference of two perfect squares. What do you notice about the numbers you CANNOT make?

A mother wants to share a sum of money by giving each of her children in turn a lump sum plus a fraction of the remainder. How can she do this in order to share the money out equally?

Can you explain the surprising results Jo found when she calculated the difference between square numbers?

Find all the triples of numbers a, b, c such that each one of them plus the product of the other two is always 2.

A 2-Digit number is squared. When this 2-digit number is reversed and squared, the difference between the squares is also a square. What is the 2-digit number?

Find the largest integer which divides every member of the following sequence: 1^5-1, 2^5-2, 3^5-3, ... n^5-n.

Which armies can be arranged in hollow square fighting formations?

There are unexpected discoveries to be made about square numbers...

What is special about the difference between squares of numbers adjacent to multiples of three?

If you know the perimeter of a right angled triangle, what can you say about the area?

Can you find out what is special about the dimensions of rectangles you can make with squares, sticks and units?

Can you find the hidden factors which multiply together to produce each quadratic expression?

Explore what happens when you draw graphs of quadratic equations with coefficients based on a geometric sequence.

Given any 3 digit number you can use the given digits and name another number which is divisible by 37 (e.g. given 628 you say 628371 is divisible by 37 because you know that 6+3 = 2+7 = 8+1 = 9). . . .

A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.

If a two digit number has its digits reversed and the smaller of the two numbers is subtracted from the larger, prove the difference can never be prime.

a) A four digit number (in base 10) aabb is a perfect square. Discuss ways of systematically finding this number. (b) Prove that 11^{10}-1 is divisible by 100.

Two cubes, each with integral side lengths, have a combined volume equal to the total of the lengths of their edges. How big are the cubes? [If you find a result by 'trial and error' you'll need to. . . .