## anonymous 5 years ago factor 225-(x+8)^2

1. anonymous

Do you know the formula of the square difference? $a^2-b^2=(a-b)(a+b)$

2. anonymous

no i wasnt aware of that one

3. anonymous

Well you should use this formula, you can rewrite your expression as: $15^2-(x+8)^2$ Now you have a=15, and b=x+8. Tell me what you think it would look like after factorization?

4. anonymous

(15-x+8)(15+X+8) ??

5. anonymous

You're smart. You just made a little mistake with a sign. Deal with x+8 as a combination at first. So when you subtract, a minus sign will go to both x and 8.

6. anonymous

HMM not sure i understand that one, thank you for the compliment btw

7. anonymous

Well, see here: $15^2-(x+8)^2=(15-(x+8))(15+(x+8))=(15-x-8)(15+x+8)$ $=(7-x)(23+x)$ And yes you really are good!

8. anonymous

ohhh i see it now witht the extra parens lol ok, haha and thanks again but your really way smarter man

9. anonymous

hey i have another one to ask if can help me still?

10. anonymous

Yeah sure, just one :)

11. anonymous

ok haha its Cos((pi/2)-x)/sin((pi/2)-x)

12. anonymous

$\cos(\pi/2-x)\div \sin(\pi/2-x)$

13. anonymous

i know i have to use the sum and difference id's for sin and cos but im hitting a wall

14. anonymous

You want to simplify: ${\cos({\pi \over 2}-x) \over \sin({\pi \over 2}-x)}?$

15. anonymous

yea the question says find

16. anonymous

It says find? A bit strange. Anyway, it clearly wants you to apply the following two formulas: $\cos ({\pi \over 2}-x)=\sin x ..(1)$ $\sin({\pi \over 2}-x)=\cos x .. (2)$

17. anonymous

Are you following?

18. anonymous

i think, would it come out to tangent?

19. anonymous

Exactly!! Didn't I just I say you're smart?!

20. anonymous

haha i try

21. anonymous

So, applying the two formulas gives: ${\sin x \over \cos x}=\tan x$ I don't know if it's giving any values for x.

22. anonymous

no it was just asking for an equal trig function, i didnt know those equations though, putting them in my notes, thanks man, youve helped me alot!!

23. anonymous

You're welcome. I am sure you're very good at math, and you pick things quickly. Good luck!!