Sept. 24 Class

Learning Goals: Factor an expression in the form of ax² + bx + c.

Today we look at how to factor trinomials in standard form with the value of a = 1.

For example, factor x² + 10x + 21.

First you check if there are any common factors.  If there is, factor them out first.  Then I introduced what I call the MAN method.

What Multiplies to the last number?  ____ x ____ = 21
What Adds to the middle number? ____ + ____ = 10
The Numbers are: 7 and 3.

Therefore, the solution is x² + 10x + 21 = (x + 7)(x + 3).

Make sure to be careful of negative factors.

Example: factor x² – 7x – 18.

M: ____ x ____ = -18
A: ____ + ____ = -7
N: -9 and 2

The factors are then (x – 9)(x + 2).



Example: factor 3x² + 12x – 15.

There is a common factor of 3.

3(x² + 4x – 5)

Now we use the MAN method on the terms inside the bracket.

M: ____ x ____ = -5
A: ____ + ____ = 4
N: -1 and 5

The factors are then 3(x – 1)(x + 5).



Homework: p. 99 #2, 3, 5-13