IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => IGCSE/ GCSE => Math => Topic started by: I Jimmy I on May 17, 2009, 02:15:47 pm

Title: Maths Doubt P4
Post by: I Jimmy I on May 17, 2009, 02:15:47 pm

Heya guyz,
I was doing Nov 2008 and I reached this question ( By the way its my first paper and I didnt study anything for business as well as Maths :D)
Anywayz its question 2.c.1
I know how to get 2x²and 16 and the -65 but from where did the 8x come from?
PLZ reply ASAP
Thank You

Title: Re: Maths Doubt P4
Post by: I Jimmy I on May 17, 2009, 02:18:26 pm

Bump!
PLZ reply, dont ignore this!

Title: Re: Maths Doubt P4
Post by: Enia on May 17, 2009, 02:25:37 pm

you should use Pythagoras' theorem. meaning side AB squared + BC squared = 9 squared.


(try to understand this because  i have no idea how to write squared on the keyboard sorry.. by (2) i mean squared)

8x comes from the squaring of (x+4)
it expands to x(2)+4x+4x+16
~~~~~~~~~~~~~~~
so then:

x(2)+x(2)+8x+16=9(2)
2x(2)+ 8x-65=0
2x(2)+8x-65=0

Title: Re: Maths Doubt P4
Post by: I Jimmy I on May 17, 2009, 02:28:52 pm

Ehhhh?
how do u get the 4x + 4x?
Cuz I already know the rest of the question, except this one...

Title: Re: Maths Doubt P4
Post by: Enia on May 17, 2009, 02:34:31 pm

by solving (x+4) squared.

That means (x+4)(x+4)

Title: Re: Maths Doubt P4
Post by: I Jimmy I on May 17, 2009, 02:45:51 pm

oooo
*sigh* Dunno wuts wrong with me...
Silly questions tbh...
Anywayz, gonna increase ur rep ;)

Title: Re: Maths Doubt P4
Post by: Enia on May 17, 2009, 03:02:30 pm

Thanks  ;D I have no idea how the -1 even happened I haven't been on this site for more than an hour xDDD