Tutoring high school math, you might be in review mode now.  The math tutor brings up a couple of factoring instances.

Instance 1:  Suppose you need to factor -2x^2 + 4x + 70.  How would you proceed?

Solution: First, you would remove the common factor (for more explanation, see my post here). However, you are best to factor out the negative 2, rather than just the 2. In general, when factoring an expression with the lead term negative, you should factor out the negative as a common factor.

We proceed:

-2x^2+4x+70=-2(x^2-2x-35)

Next, we factor the inside expression using the easy trinomial method.

-2(x^2-2x-35)=-2(x-7)(x+5)

Sometimes you encounter an expression with just a negative in front.

Instance 2: Factor -x^2 +10x – 24

Solution: First, factor out the negative:

-x^2+10x-24=-(x^2-10x+24)

Now, factor inside, using the easy trinomial technique:

-(x^2-10x+24)=-(x-6)(x-4)

I’ll be mentioning more little tips and tricks the next few posts, with the hope of refreshing the skills towards first semester exams:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.