Solving Quadratics by Factoring

In order to find the zeros or the x intercepts in standard form, the equation must be factored [(x+r)(x+s)]. If not you must put it in factored form (review lesson on factoring simple and complex trinomials). From there it becomes really easy to find the x-intercepts. Let’s see how…

Let’s do an example…

Put the equation y = x^2 + 5x + 6 in factored form.

y = x^2 + 6x + 5

y = (x + 1)(x+6)

From there we have to sub 0 in for y because as we all know to find the x-ints y must equal 0.

y = (x + 1)(x+6)

0 = (x + 1)(x+6)

Then we set each bracket equal to zero, making sure that we remove the brackets at the end, so we end up with…

x + 1 = 0

x+6 = 0

We then want to isolate for x, for that we must bring the numbers over to the other side and subtract 0 by them.

x = -1

x= -6

So therefore, our x-ints are (-1, 0) and (-6, 0)

Now you try…

Find the zeros for the equation y = x^2 + 2x – 15

**Remember to put it in factored form and then solve for the x by setting each bracket equal to zero**

Answer…

X ints: (-3, 0) and (5, 0)

Extra Practice…

A Video for Extra Help…