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raghavs
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ssy84
ANSWER TO Q2

It helps if you actually draw this out. The circle will have its origin at 0, and touch on points 1 and -1 on the x axis and 1 and -1 on the y axis

1) Insufficient as the line can either pass through or not pass through the circle. Try drawing it and see. You need the slope to find out if line k will intersect the circle.

2) With this slope, you either go left by one unit and up by 10 from any point on the x axis, and/or go right by one unit and go down by 10 from any point on the x axis. Either way, the line WILL pass through the circle. I'm not sure how to prove this mathematically though. It would help if someone could explain.

As I said, it helps if you draw it out.

I have to disagree with your solution. No matter what the slope is, it’s possible for line not to cross the circle as the x intercept can be + infinite. Answer is definitelly E.

(1) Just says that x intercept is right to the circle --> not sufficient
(2) Just says that slope is -1/10 --> line is just going down. --> not sufficient.

(1)+(2) As we don't know exact intercept of line and X-axis we can not determine whether line intersects the circle or not.

E.
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Here is my approach.

Let the equation of the line be y = mx + c where m is the slope and c is the y intercept. Now we need to find whether this line intersects the circle with Center O and radius 1. It means we need to find whether X / Y intercept is <= 1. Only then can a line intersect the circle.

Clue 2 - (I am considering clue because it looks simple. )

Given slope is -1/10 ==> m = -1/10. Nothing about the X / Y intercept is known. Hence we cannot find how the line is inclined and where on the X and Y axis is the line intersecting. Hence the clue is insufficient.

Options B and D out.

Clue 1: Given x-intercept > 1. No information about the slope of the line is given. Hence we cannot find how the line is inclined and where on the X and Y axis is the line intersecting. Hence the clue is insufficient.

Option A is out.

Consider both the clues.

Slope is given. m = -1/10
X intercept is given == -c/ m > 1 ==> 10C > 1 (substituing the value of m) ==> c > 1/10.

We can derive that y intercept is > 1/10

So we can conclude that x intercept > 1 and y intercept is > 1/10 But cannot definitely say whether y intercept is >1 or not. Hence both the clues are also NOT sufficient.

Ans E.

Remember : in order to know the how the line is inclindes, we always need two values.
a) Slope of the line
b) X / Y intercept. (This should the exact value not the range / ineqaulity.
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thanks for the breif expl. :)

Regards
Raghav
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ssy84
ANSWER TO Q3:

Firstly, note that the equation y=(x+a)(x+b) is a parabola. It will intersect the x-axis at two points.

Statement 1
We can't do anything with this equation. Combined with the equation given in the stem of the question, thee are still 4 variables and only 2 equations.

Statement 2
This means x =0, y=-6. Plugging this into the original equation:
-6=(0+a)(0+b)
-6=ab
Possible values of a and b can be: (6,-1), (-1,6), (3,-2), (2,-3). There is insufficient information to determine which exactly set of values of a and b we should choose however.

Statement 1 and 2 combined
A+b=-1
-6=ab
A unique pairing of a,b can be determined : -3, 2

Note that we are just asked to find the points at which the graph intersects the x-axis. We do not need to know exactly which value is a or b. A can be -3 or 2 and vice versa for b.

So, (x-3)(x+2)=y
To find the point of intersection, let y=0 and solve accordingly:
X-3=0, x=3
X+2=o, x=-2

The graph will intersect at (3,0), (-2,0)

Both statements are sufficient.


who said that a & b were integers???
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totally agree with E for Q2...

Was it a real gmat official question? Wow... this sucks !!


For Q3 answer is III the only way K can intersect the x-axis in when X > 0
The bigger the slope, the lower the x-intersect
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ssy84
ANSWER TO Q2

It helps if you actually draw this out. The circle will have its origin at 0, and touch on points 1 and -1 on the x axis and 1 and -1 on the y axis

1) Insufficient as the line can either pass through or not pass through the circle. Try drawing it and see. You need the slope to find out if line k will intersect the circle.

2) With this slope, you either go left by one unit and up by 10 from any point on the x axis, and/or go right by one unit and go down by 10 from any point on the x axis. Either way, the line WILL pass through the circle. I'm not sure how to prove this mathematically though. It would help if someone could explain.

As I said, it helps if you draw it out.

I don't understand how the slope could be 1/10. I thought the slope would be -6. Could you please explain to me how you came up with that?

Thanks in advance

Mari
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Please post one question per topic.

Topic is locked. Please continue discussions in the below topics.
Question #1: ds-coordinate-geometry-97403.html
Question #2: does-line-k-touch-circle-or-not-101471.html
Question #3: xy-plane-71492.html and gmat-prep-question-any-shortcuts-88398.html



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