Qualification > Math

Maths Doubt P4

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I Jimmy I:
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

I Jimmy I:
Bump!
PLZ reply, dont ignore this!

Enia:
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

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

Enia:
by solving (x+4) squared.

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

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