The best way to solve a quadratic function is to put brackets into the equation.

Start with an example

Find x when y=0 for the function

y=x*2 + 5x + 6

As y=0 make the whole equation= 0:

x*2 + 5x + 6=0

Try and put this into brackets:

(x+a)(x+b)=0 (as all the values are positive, we know that there are going to be no negative signs in the brackets).

Now we just need to find values for a and b that multiply out to give us the equation we need.

Try a=6 and b=1:

This gives us the 6 at the end but when multiplied out gives us 7x- which is too much.

Now try a=2 and b=3 and multply out:

We get 0=x2+ 2x + 3x + 6= x2 + 5x + 6 ... which is what we want!

So we get (x+2)(x+3)=0

For it to equal 0 either:

x+2=0 so x=-2 or

x+3=0 so x=-3

so x=-2, -3

Make a the subject of the formula f=(a+1)/2