## Inopeki Group Title FOILing, do i multiply or add? Like (2x+4)+(2x+4) i add there, right? And (2x+4)*(2x+4) I multiply there, right? 2 years ago 2 years ago

1. satellite73 Group Title

yes

2. Inopeki Group Title

I did that in class todya but i didnt get the right answer..

3. satellite73 Group Title

what did you get for the first one?

4. Inopeki Group Title

(2x+4)+(2x+4) 4x+2x+4+4+2x+4+4 8x+16

5. satellite73 Group Title

hmm

6. satellite73 Group Title

7. amistre64 Group Title

when it says to add, I would add. and when it says to multiply, id multiply. but thats just me set in my ways :)

8. satellite73 Group Title

$(2x+4)+(2x+4)=2x+4+2x+4=2x+2x+4+4$

9. satellite73 Group Title

let's imagine for a moment that x was ten (x is a variable, but it could be ten) then $2x+4=2\times 10+4=24$ and $24+24=48$

10. Inopeki Group Title

I thought it was like this |dw:1327066387934:dw|

11. satellite73 Group Title

multiplication distributes over addition. so if you had $(2x+4)(2x+4)$ you would use the distributive law, just like if you had $24\times 24$

12. Inopeki Group Title

But wheres the x?

13. Tomas.A Group Title

addition is commutative you can remove brackets when you have ONLY addition

14. satellite73 Group Title

but addition is the same as "combine like terms" just as you would with arithmetic 24 + 24 ______ 48 2x + 4 + 2x + 4 __________ 4x + 8

15. amistre64 Group Title

2x+4 (+) 2x+4 -------- 4x+ 8 2x+4 (x) 2x+4 --------- 8x+16 4xx+8x ----------------- 4x^2+16x+16

16. Inopeki Group Title

Why would it be 4x^2+16x+16?

17. satellite73 Group Title

@inopeki i was making an analogy. the work you do with variables is a generalization of the work you do in arithmetic, and if it doesn't work with arithmetic it certainly doesn't work with variables, because the variable could be a number, that is you could replace the variable by a number

18. amistre64 Group Title

becasue thats what happens when you multiply stuff

19. Inopeki Group Title

Oh ok

20. Inopeki Group Title

so basically just add them up?

21. Inopeki Group Title

2x+4 (+) 2x+4 -------- 4x+ 8

22. satellite73 Group Title

imagine your job was to add $24+24$\ what would you do? line them up and add

23. amistre64 Group Title

5+3 = 8 (x) 2+4 = 6 ------------ 20+12 10+6 -------------- 10+26+12 = 48

24. Inopeki Group Title

24 +24 ---- 48

25. satellite73 Group Title

and similarly 2x + 4 + 2x + 4 __________ 4x + 8

26. Inopeki Group Title

Oh! Give me another example?

27. satellite73 Group Title

$(3x+5)+(4x+1)$

28. Inopeki Group Title

(3x+5) +(4x+1) -------- 7x+6

29. satellite73 Group Title

that's it!

30. Inopeki Group Title

Yes! :D Thanks