# Thread: Little Bits and Bobs!

1. ## Little Bits and Bobs!

Hey, is: 2(4-y) a product? How will i be able to tell??

2. I'm doing expressions: and i know that the first term in the brackets you multiply that by the closesed whole number immediatly beside it, and stuff!
(example: 2(s + 4)=2s + 8)
but for this: 4(9 - y) what would i do?

3. and also, with: 3(d + e) since there is no number where the "e" is situated!

4. Originally Posted by Sazza
Hey, is: 2(4-y) a product? How will i be able to tell??
A "product" is defined to be the multiplication of two numbers. 2 and 4 - y are numbers. Thus this is the product of 2 and 4 - y.

-Dan

5. Originally Posted by Sazza
I'm doing expressions: and i know that the first term in the brackets you multiply that by the closesed whole number immediatly beside it, and stuff!
(example: 2(s + 4)=2s + 8)
but for this: 4(9 - y) what would i do?
This deals with the "Distributive Law of Multiplication Over Addition" (Yes, I know you are subtracting, but adding and subtracting are substantially the same process.) This law says if we have the three numbers a, b, and c that:
a*(b + c) = a*b + a*c
or
(a + b)*c = a*c + b*c
(For technical reasons there is a difference between the two statements. If a, b, and c are real numbers and "+" and "*" are ordinary addition/subtraction and multiplication respectively then the two statements are identical.)

4(9 - y) = 4(9 + (-y)) = 4*9 + 4*(-y) = 4*9 - 4*y = 36 - 4y

-Dan

6. Originally Posted by Sazza
and also, with: 3(d + e) since there is no number where the "e" is situated!
Like the last problem:
3(d + e) = 3*d + 3*e = 3d + 3e

-Dan

7. 2ab + 3a-ab! Does that equal 5ab? Because i'm not sure weather to include the a.?? or is it 5ababa???

8. Originally Posted by Sazza
2ab + 3a-ab! Does that equal 5ab? Because i'm not sure weather to include the a.?? or is it 5ababa???
You can only add "like" terms together. So if the variables don't match EXACTLY you can't add them. You have
2ab + 3a - ab

We can only subtract the ab from the 2ab. The 3a has no matching term. So this is:
2ab + 3a - ab = 2ab - ab + 3a = (2ab - ab) + 3a = ab + 3a

-Dan