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the equation

by coolly01 » Fri Apr 08, 2011 8:12 am
Hi guys, try this !!, I took it wrong

In the equation y2 + ay - 24 = 0, a is a constant and y is a variable. What is the value of a ?

(1) y + 8 is a factor of y2 + ay - 24

(2) 3 is a root of the equation y2 + ay - 24 = 0

[spoiler]OA: D[/spoiler]
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by HSPA » Fri Apr 08, 2011 8:23 am
-8, 3 are the roots... what you took wrong.. OA looks okay..
Your intented question please...
First take: 640 (50M, 27V) - RC needs 300% improvement
Second take: coming soon..
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by manpsingh87 » Fri Apr 08, 2011 8:31 am
coolly01 wrote:Hi guys, try this !!, I took it wrong

In the equation y2 + ay - 24 = 0, a is a constant and y is a variable. What is the value of a ?

(1) y + 8 is a factor of y2 + ay - 24

(2) 3 is a root of the equation y2 + ay - 24 = 0

[spoiler]OA: D[/spoiler]
Thanks
y^2+ay-24=0 is a quadratic equation in y.!!
1) as y+8 is a factor of y^2+ay-24, therefore at y=-8 quadratic equation becomes zero. therefore on substituting y=-8 we have (-8)^2+a(-8)-24=0; 40-8a=0, a=5

2) similarly here put y=3 and find the value of a..!!

hence D
O Excellence... my search for you is on... you can be far.. but not beyond my reach!
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by coolly01 » Fri Apr 08, 2011 8:47 am
LOL, how crazy I was !!!!!!
I picked option B, coz in (1) y + 8 is a factor of y2 + ay - 24,
I almost forgot that y2 + ay - 24 = 0, So I just kept in my mind a statement that
y2 + ay - 24 is divisible by (y + 8) and totally ignored that y2 + ay - 24 = 0

Let's try this problem guys, a tougher one. I also took it wrong.

A circular Jacuzzi, X has 1/4 the circumference of the circular pool, Y. Each structure is surrounded by a tile border with neglible width. What is the surface area of Jacuzzi X?

(1) The surface area of Y is 900Ï€ square feet.

(2) The length of the border immediately surrounding Y is 60Ï€ ft.

[spoiler]OA: D[/spoiler]

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by clock60 » Fri Apr 08, 2011 11:32 am
i`ll try to answer on 2 problem
if l(x)=2*pi*r, and l(y)=2*pi*r1, and given that
2*pi*r=2*pi*r1*(1/4)
r1=4r, we need to find S(x)=pi*r^2, it is clear that if we find r or r1, we can answer on the question

(1)pi*r1^2=900*pi, r1=30 from here we can find r, and find the area of the circle
(2)2*pi*r1=60*pi, again r1=30 and also possible to find r and area
D seems right
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by HSPA » Fri Apr 08, 2011 7:11 pm
Let radius of X = r and radius of Y = R

R/4 = r;

1) pi * R^2 = 900pi; we can determine pi* r^2;900pi/16
2) 2*pi*R = 60pi; we can determine pi*r^2
First take: 640 (50M, 27V) - RC needs 300% improvement
Second take: coming soon..
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