Factoring a Polynomial

Date: 04/06/97 at 20:05:18
From: amanda butts
Subject: Factoring a Polynomial

How do I solve 3y^2+12y = 0 ?

Date: 04/07/97 at 20:15:01
From: Doctor Mike
Subject: Re: Factoring a Polynomial

Dear Amanda,
   
You have probably seen the Distributive Law.  One of several versions
of it is (A + B)*C = A*C + B*C.  You can apply this to the left side 
of your equation, because y^2 is really y times y.  It becomes : 
  
       (3y + 12)*y = 0
  
We have not changed the equation much; just factored the left side.
  
Now what?  In order for y to be a solution to this equation, one of
the 2 things multiplied on the left must be equal to zero.  So, that
means y=0 will work.  But how do you choose y so that 3y+12 is zero?
This is a simpler kind of equation that you have seen before.  If you
solve that equation for y, that will give you the other solution.
Hint: the second solution is a negative number.  Good luck.
   
I hope this helps.

-Doctor Mike,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/