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shivanigs: Junior | Next Rank: 30 Posts; Posts: 22; Joined: Fri Apr 27, 2012 5:10 amFollowed by: 2 members

by shivanigs » Tue Oct 02, 2012 11:08 pm

Hi,

Request help with the following problem.Thanks..

Which one is the equation for the given parabola ?(image attached -P.S. - unable to draw a curved line hence used an oval shape,kindly ignore the curve above,the parabola is opening upward and is at the point -4 on the x - axis)

1. y = x+4
2.y = x-4
3.y = (x+4)^2
4.y= (x-4)^2

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Source: Beat The GMAT — Problem Solving | Tue Oct 02, 2012 11:08 pm

das.ashmita: Master | Next Rank: 500 Posts; Posts: 118; Joined: Mon May 21, 2012 10:07 pmFollowed by: 4 members; Thanked: 23 times

by das.ashmita » Tue Oct 02, 2012 11:19 pm

Hi shivanigs

I'll try to answer

The equation of a parabola must have a square term. So eliminate (1) & (2)

Its given that it meets x axis at -4
That is, when y=0, x=-4
Option (3) satisfies
y = (x+4)^2
=> 0 = (x+4)^2
=> |(x+4)| = 0
=> x = -4

Hence 3

Hope it helps

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Javoni: Junior | Next Rank: 30 Posts; Posts: 24; Joined: Sat Jul 09, 2011 1:45 pm; Location: Tajikistan, Dushanbe; Thanked: 2 times

by Javoni » Fri Oct 05, 2012 10:35 pm

Here we go,

It is straightforward, like this:

Since from your drawing we get that if x = -4, y = 0, hence the answer must be either (1) equation or (3) equation, but as we see the first one is not parabola at all, just straight line, hence it is (3) equation the correct answer. More importantly, according to our parabola y >= 0 so go with (3). Best approach is picking number, and knowing x=-4 makes the process easier..

shivanigs wrote:Hi,

Request help with the following problem.Thanks..

Which one is the equation for the given parabola ?(image attached -P.S. - unable to draw a curved line hence used an oval shape,kindly ignore the curve above,the parabola is opening upward and is at the point -4 on the x - axis)

1. y = x+4
2.y = x-4
3.y = (x+4)^2
4.y= (x-4)^2

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pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

by pemdas » Sat Oct 06, 2012 1:22 pm

generally y=x^2 means you have symmetry around the y-coordinate line with a vertex of the function's graph in the coordinate plane origin point (0,0). Here you have shift x=-4 or (x+4)=0 with function defined as y=(x+4)^2, hence pick option 3.

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