Qualification > Math

maths again!!!

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nid404:
I got the part where you need to find the domain and the range but i don't  get how to show the Area is 36-(6-w)^2

I'll put down the other part tho.....but u must wait till astar confirms the answer
We need to evaluate the equation for any real number....but area cannot have a negative value, so can't w
so
36-(6-w)^2>0
36-(6-w)^2<24w(it's 24m..u made a typo)
so this gives us...
0<w<12 domain

After that you try finding values of A between values of w 1-11
you'll notice
0<A<36 is the range....

if you didn't get it...i don't mind explaining it again....
I'll try figuring out the proving part too...

Ghost Of Highbury:
proving part

lenght = x

width = w

wx = area

2w + 2x = 24

2x = 24 - 2w

x = 12 - w

area = wx = 12w - w2

----------
36 - (6-w)2 = 36 - (36 - 12w + w2)

==> 36  - 36 +12w -w2
= 12w - w2

-----------
done..

nid404:
why did u take
2w+2x=24
this means twice width + twice length= length....can u explain this

Ghost Of Highbury:

--- Quote from: nid404 on September 21, 2009, 04:12:42 pm ---I got the part where you need to find the domain and the range but i don't  get how to show the Area is 36-(6-w)^2

I'll put down the other part tho.....but u must wait till astar confirms the answer
We need to evaluate the equation for any real number....but area cannot have a negative value, so can't w
so
36-(6-w)^2>0
36-(6-w)^2<24w(it's 24m..u made a typo)
so this gives us...
0<w<12 domain

After that you try finding values of A between values of w 1-11
you'll notice
0<A<36 is the range....

if you didn't get it...i don't mind explaining it again....
I'll try figuring out the proving part too...

--- End quote ---

the domain part can also be explained this way

first simplify 36-(6-w)^2 ==> 12w - w2

the area has to be greater than 0

thus, 12w - w2 > 0

12w > w2

w2 < 12w

w < 12

therefore..........0<w<12

-------------------------------------

Ghost Of Highbury:

--- Quote from: nid404 on September 21, 2009, 04:29:34 pm ---why did u take
2w+2x=24
this means twice width + twice length= length....can u explain this

--- End quote ---

the length of the wire = 24 ...

therefore the permieter of the rectangle is also = 24

perimeter of a rectangle = 2(length) + 2(width) = 2x + 2w = 2w + 2x

thus, 2w + 2x =24

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