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Yep C, This topic really shouldnt have so many posts. This is a very simple question. You have no information on y, hence y could have been zero and that can only be averted with the presence of statment 1.
We know from the question stem that x is a positive integer.
In statement 2 why don't we account for: x-1 = -4 ==> x = -3 and x-1 = 4 ==> x = 5 This would yield E as the answer. Am I missing something?
Ya Since it's given question stem that x is +ve, we need not consider the -ve value of x so the vale of x we will take the value of x as 5 and the the value of the expression will come y to the power 2 multiplied with 121 Now Y has the roll, suppose it's less then 1 say .1, the value of the entire expression will be 1.21 which is less than 75 , so the value of y has to be more than 1 or less than -1 to yield the the value of the expression >75
I think the answer/ explanation of this question is wrong.
Here is the official explanation: --------------------------------------------- We need to know two things here
The value of x Whether y is greater than 1 From S1, we only know that y>1
From S2, we only have the value of x. we also know that x is positive. So, we have to only consider the positive root. Combining the two statements, we have the required information. The correct answer is C. ------------------------------------------------ However, i think the answer is E, since we dont have any information on whether y is an integer or not. It can be possible that y is a fraction. Am i missing something guys????
Jimmie Jaz is correct; the answer is E. True, Y is greater than 1 but if Y were a very small fraction (i.e. 1001/1000, 1.001) then raised to the 242 power the product would still be less than 75.
1.001^242= 1.27 1.27<75 Statement's 1 and 2 are Insufficient. E
Given Statement 1 y>1 and x is a positive integer. So x could be any value from 1 onward. depending on the value of x, the vale of equation changes. so we do no get a concrete value.
Statement 2 (X-1)^2=16 from this equation we got two values of x i.e 5 and -3 discard the -ve value of x, because it is given in the queston y^2(5^3-5+1)= y^2(121). still we don't know the exact value if y is 0, then we get 0<75 of if y is fraction we get different values for different values of y so statement 2 is also not sufficient Combine statement 1 and 2 we get the vale of equation 121 or more i.e >75 so C is the right answer Give Kudos, If you like my post
Last edited by daboo343 on 06 May 2014, 02:27, edited 2 times in total.
Bunuel,Can you please help. I believe the answer should be E. Since,y >1. It is not given that y is integer.3
from Statement 1,we know y>1.:- If we consider y=1.1 then the y^2(x^3-x+1)>75 is true. If we consider y=2,the y^2(x^3-x+1)>75 is false.
Thus both the statements doesn't help to come to a definite answer.
If x is a positive integer, is y^2(x^3-x+1)>75?
(1) y>1. No info about x. Not sufficient.
(2) (x-1)^2=16. Take the square root: |x-1|=4 --> x=-3 or x=5. Discard the first root because we are told that x is a positive integer, so we have that x=5. Thus the question becomes: is 121y^2>75? If y=0, then the answer is NO but if y=1, then the answer is YES. Not sufficient.
(1)+(2) From (2) the question became: is 121y^2>75? (1) says that y>1. For any y greater than 1, 121y^2 will be greater than 75. Sufficient.
Statement 1 The inequality cannot be uniquely evaluated with only information: x >0 and y > 1.....Not sufficient......A B C D E
(x-1)^2=16 Or,|x-1|=4 Or, x=5 [ The other solution of x = -3 is discarded as x > 0]
Substituting x=5 and (x-1)^2 =16 into the expression x^3-x+1 ,
x^3-x+1 = (x+1)(x-1)^2= 5*16=80
As no information on y is available, the inequality y^2(x^3-x+1)>75 can not be uniquely evaluated......Not sufficient...AB C D E
Using both statement (1) and (2), it is possible to evaluate the expression y^2(x^3-x+1) or (y^2) * 80 to be always greater than 75 even for the minimum value of y......Both statements together is sufficient...............ABCDE