Factorising quadratics - (easy) Example 2
Factorise the quadratic `x^2-9x+20=0`
The factors of 20 are:
1 and 20
2 and 10
4 and 5
Now ask yourself what factors of `c` add to give `b`.
i.e. what factors of `20` equal `-9`.
Can be written as:
Check by multiplying out:
The roots of `x^2-9x+20=0`
Now solve for `x`
`x=4` or `x=5`
The roots of `x^2-9x+20=0` are `x=4` or `x=5`