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2 Math Doubts - Tricky !!

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2 Math Doubts - Tricky !!

by mohit11 » Sat Feb 13, 2010 12:30 am
1) Can someone if there is a condition where a-b/c =0 does not equate to a-b = 0 , i can think of C= 0, which would make L.H.S infinity.


2) OG 10 - 173.

IS Y=6

1)Y^2 = 36
2)Y^2 - 7Y+ 6 = 0


OA is C

Please give why OA is C, 1) Yiels 2 roots, 2) Yields, 1 root same as 1) and another root.
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by Brent@GMATPrepNow » Sat Feb 13, 2010 9:17 am
mohit11 wrote:1) Can someone if there is a condition where a-b/c =0 does not equate to a-b = 0 , i can think of C= 0, which would make L.H.S infinity.

2) OG 10 - 173.

IS Y=6

1)Y^2 = 36
2)Y^2 - 7Y+ 6 = 0

OA is C
Please give why OA is C, 1) Yiels 2 roots, 2) Yields, 1 root same as 1) and another root.
1) If (a-b)/c = 0 then the only possibility is that a-b=0


2) Is y=6?
1) y^2 = 36
2) y^2 - 7y+ 6 = 0

1) y^2 = 36 --> y=6 or y=-6 INSUFFICIENT
2) y^2 - 7y+ 6 = 0 --> (y-1)(y-6)=0 --> y=1 or y=6 INSUFFICIENT

(1&2) if both statements are true then the only possible value for y is 6 . . . SUFFICIENT
Last edited by Brent@GMATPrepNow on Tue Jan 31, 2012 12:13 pm, edited 1 time in total.
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by mohit11 » Sat Feb 13, 2010 9:31 am
Thanks brent. It is an elementary concept but had a small doubt, but (1&2) if both statements are true kinda resolved the doubt.

I was thinking.

1) gives 2 roots A and B

2) gives 2 roots A (common from (1) ) and C

So if we consider them together, then there are 3 roots, A,B and C, but like you rightly pointed out both statement are true and only A would satisfy both the equations :)
Last edited by mohit11 on Thu Feb 18, 2010 7:14 am, edited 1 time in total.
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by harsh.champ » Thu Feb 18, 2010 7:06 am
Brent Hanneson wrote:
mohit11 wrote:1) Can someone if there is a condition where a-b/c =0 does not equate to a-b = 0 , i can think of C= 0, which would make L.H.S infinity.

2) OG 10 - 173.

IS Y=6

1)Y^2 = 36
2)Y^2 - 7Y+ 6 = 0

OA is C
Please give why OA is C, 1) Yiels 2 roots, 2) Yields, 1 root same as 1) and another root.
1) If (a-b)/c = c then the only possibility is that a-b=0


2) Is y=6?
1) y^2 = 36
2) y^2 - 7y+ 6 = 0

1) y^2 = 36 --> y=6 or y=-6 INSUFFICIENT
2) y^2 - 7y+ 6 = 0 --> (y-1)(y-6)=0 --> y=1 or y=6 INSUFFICIENT

(1&2) if both statements are true then the only possible value for y is 6 . . . SUFFICIENT
Hey Brent,
I didn't get the 1st part.
If a-b=0 and suppose c=3 ,then (a-b)/c = 0 but a-b=0[but in the question we are given that the R.H.S. should not be zero]

Also,can't we put c= infinity and a-b=3
then the LHS would be zero and (a-b) would not equate to zero.

Can u plz clarify??
I am very confused over here.
Thanks in advance.
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by shashank.ism » Thu Feb 18, 2010 9:23 am
mohit11 wrote:1) Can someone if there is a condition where a-b/c =0 does not equate to a-b = 0 , i can think of C= 0, which would make L.H.S infinity.


2) OG 10 - 173.

IS Y=6

1)Y^2 = 36
2)Y^2 - 7Y+ 6 = 0


OA is C

Please give why OA is C, 1) Yiels 2 roots, 2) Yields, 1 root same as 1) and another root.
1). I am confused whether it is a-b/c = 0 or (a-b)/c = 0 .. In any case if a-b/c= 0 ---> b=ca
if (a-b)/c = 0 --> a-b= 0 --> a=b ..why are u trying for c--> 0 ..it is not required anyway here.

2) st.1 : Y^2 = 36 --> Y=+/- 6 as square of both will give 36 ---not sufficient
st.2 : Y^2 - 7Y+ 6 = 0 --> Y^2 - 6Y-Y+ 6 = 0 --> (Y-1)(Y-6) =0 --> Y=1,6 ---not sufficient

combined it gives value as Y=6 so --- sufficient Ans C
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