30b^2+48b-24

Question

30b^2+48b-24

anonymous · Answer

What are you trying to do with this expression?

anonymous · Answer

Well, it can be factored:$$6 (b+2) (5 b-2) $$

myininaya · Answer

@robtobey Please walk the person through the problem or at least provide an explanation of how you got that.
Thanks.


So what do 30,48,and 24 have in common:  6
since 
30=6(5)
48=6(8)
24=6(4)
-------
So we know we can factored 6 out like so:

$$6(5b^2+8b-4)$$

Now lets look at $$5b^2+8b-4$$

We can do trial factors or do the factor by grouping way.
I like the factor by grouping way.

a=5,b=8,c=-4

We need to find two factors of a*c that have product a*c and sum b

So 
a*c=5(-4)=-20

What are two factors of -20 that have product -20 and sum 8.