The Quadratic Formula

There is a nice formula for finding the roots (zeroes, ”where the graph crosses
the x-axis”). The idea is that given a quadratic polynomial :

We can say the roots occur at:

We could plug this back into our equation and see that we do indeed get zero,
but for now, I will ask you to just believe me.


Find the roots of the polynomial y = 2x2 − 6x + 4.
To do this, we see we can simply apply the given formula to get:

We notice that plugging in the values of x = 2 and x = 1 do indeed give us zero,
this makes us happy.

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