CPhill

Suppose we want the LCM  for 60 and 42

"Prime factor" each

60  = 2^2 x 3 x 5

42 = 2 x 3 x 7

Put the like prime factors over each other like this:

2^2      3       5

2         3               7

Select the different factors with the highest powers....if the same factor has the same power, select either one.....so we have....

2^2, 3, 5, 7       multiply these together

4 x 3 x 5 x 7 =  420   and that's the LCM

Here's an "interactive" site for this  :   http://www.mathopenref.com/trapezoidarea.html

Pretty neat, huh ???

Factors of 60   =

2 3 4 5 6 10 12 15 20 30

Factors of 42  =

2 3 6 7 14 21

6 appears to be the GCF

No.....that was just an example problem

7a2 - 6a + 2a2 + 5a

7a^2 + 2a^2     = 9a^2

-6a + 5a = -1a

So the answer to your question is :

9a^2  - 1a

No....that's not quite correct....let's look at this....step-by-step

7a2 - 6a + 2a2 + 5a

7a^2 + 2a^2     = 9a^2

-6a + 5a = -1a

I see what's giving you problems...it's the signed numbers......let me help you with this

If we have the same signs......we just add the two numbers and keep the sgn.....for instance..

 3a + 7a =  10a    remember...if there s no sign in front of the number....it's assumed to be positive

Also

-6d - 4d   =  -10d

If we have different signs, here's the trick :

-9a + 3a

"Forget" the signs

Take the "larger" number and subtract the "smaller" number

The "larger" number here is 9   the "smaler"  is 3

Subtract      9 - 3 = 6

What sign was on the larger number???   It was  negative......so that's the sign we use in the final answer  = -6a

One more

8w - 3w

8 is the larger number.....3 is the smaller    8 - 3 = 5    so  .....   5w   is our result

See how to do this ???

7a^2 - 6a + 2a^2 + 5a

Remember that we can only add / subtract variables of like powers....let's put those together........

What's    7a^2 + 2a^2     ???

What's  -6a  + 5a   ???

Post your answer......let's see what you have.....

Hey.....you got it  !!!!!

-2r - 9t   !!!!

Well done.....!!!!

OK.....that's good for the second part.....

What's 6r - 8r  ????

6r - 5t - 8r - 4t

OK.......what is the result of this  ???

6r - 8r       ????

And what is the result of this??

-5t - 4t    ????

Combine the results amd post your answer.......don't worry if you make a mistake....we'll work through it   !!!!

Oops, sorry....yep....1r....I'll make the correction....!!!!