It's called the "zero-factor property", and it is common sense:

The principle is this:

If two quantities are multiplied and their product is 0, then one of 
them must be zero:

You have this:

                     (a+1)(a+2) = 0

This has two quantities (a+1) and (a+2) multiplied together and that
product equals 0.  Therefore there are two possibilities:

1.  (a+1) is 0 
2.  (a+2) is 0

Realize that unless one of those equals zero the product would not equal 0.



So to get both possible answers we set each  DISABLED_event_one=  0

      Setting a+1 = 0, subtracting 1 from both sides gives a = -1 

      Setting a+2 = 0, subtracting 2 from both sides gives a = -2

Therefore there are two possible solutions a = -1 and a = -2.

---------------------------

                          n²+3n-12 = 6

Get 0 on the right by adding -6 to both sides:

                          n²+3n-18 = 0

Factor the left side

                        (n+6)(n-3) = 0

As above to get both possible answers we set each  DISABLED_event_one=  0

      Setting n+6 = 0, subtracting 6 from both sides gives n = -6 

      Setting n-3 = 0, adding 3 to both sides gives n = 3

Therefore there are two possible solutions n = -6 and n = 3.

Edwin

 

Hi,

If (a+1)(a+2) = 0

Then

(a + 1) = 0

    a = -1

or

(a + 2) = 0

   a = -2

If (a+1)(a+2) = 0,  then a = -1   or a = -2



n^2 + 3n -12 = 6

n^2 + 3n -18 = 0

factoring:

(n + 6)(n - 3) = 0

AND

(n + 6) = 0

or

(n - 3) = 0

  n = -6   or n = 3 

Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!
 You need extra help if you have to do 

this stuff & you're confused.



----------------------

There's a method called FOIL, which means

First

Outer

Inner

Last

-----

First is 

Outer is 

Inner is 

Last is 

--------------

Now just add them up



 answer

Now set it equal to 



This is the equation, but as far as solving it

just go back to 



You've got ( something) x ( something ) = 0

Either one or both of the somethings has to be 

for this to be true, so I'll say





and, I'll say





So, a = -1 and a = -2 are the solutions

--------------------------------

Now If I plug these into the equation I came up with, it

should be true











OK

Seriously, don't stay confused- get help! 

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