Factorising

[RossiJ]

Keep making silly mistakes with my method currently (the cross multiplying method kind of thing haha)

anyone want to help me out with the easiest factorising method (not including Pythagoras theorm)

Ta x

[dc302]

Completing the square takes a while but it will never go wrong! Also, it helps a lot to expand again after you factorise it, just to check if you've done it correctly.

[Kingofrok33]

Here's an example:

3x^2 +5x - 2

Usually I would just find which two numbers equal the the end number when multiplied with the first number, and equal the middle number when added together. So in this case, 3 times -2 = -6, which can be made by 6 and -1. These two numbers also add up to +5, so it works.

Then: 3x^2 + 6x - x - 2

Then you factorise each half, making sure that the numbers in the brackets are the same, ie:

3x(x + 2) - 1(x + 2)

The factors then simply are (3x-1) and (x+2). This might look long and pointless, but it's fairly easy to work through and gets it right every time.