Factorise x² + x - 20

Find two numbers that when multiplied will give you 20 but when added will give you 1.

The factors of 20 are: 20 x 1, 10 x 2, 5 x 4. Which set of numbers do you think would work?

5 and 4 perhaps?

you need to ADD the two numbers so that their sum will be +1. How about +5 and -4?

So your factors are written this way (x + 5)( x - 4). OK?

You first have to figure that you are going to have an x on each side. so it will look like this right away (x+__) (x-__) You have to have the plus and minus because you have a -20. Now you have to figure out what times what equals 20. You can have 10 and 2 or 4 and 5. To get positive 1x you need the 4 and 5 so the final factorial will look like this (x+5)(x-4). Good luck in math!

x² +5x -4x -20
x(x+5) -4(x+5)
(x-4)(x+5)

x² + x - 20

= x^2+5x-4x-20

=x(x+5)-4(x+5)

=(x+5)(x-4)