If ((t^2)-1)/(t-1)=2, then what value(s) may t have?
A) 1 only
B) -1 only
C) 1 or -1
D) no values
E) an infimite number of values
GMAT Question of the Day: Algebra
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the equation can be written as
t^2-1 = t-1
t^2-t=0
t(t-1) = 0
so t can have values 0 or 1;
There is no choice available for these choices.
therefore My choice is A.
Krishna I got the same too.. but if we substitue t=1 the eqn doesn’t evaluate to 1. Hence I guess D) no values
If not some one please explain.
t^2 -1 / t-1 = 1
=> t^2 – 1 = t-1
=> t^2 = t
This can be true only when t = 0 OR t = 1 but with t=1, the equation doesn’t stand valid, so t can only be 0 (which is not an option).
Alternative way
(t^2-1)/(t-1) = (t-1)(t+1)/(t-1) = (t+1) = 1 => t=0
ohhhhhhh Sorry for typo.
Correct one is this
If ((t^2)-1)/(t-1)=2, then what value(s) may t have?
A) 1 only
B) -1 only
C) 1 or -1
D) no values
E) an infimite number of values
No Values
Ans is A?
[t^2 -1 / t-1 = (t+1)(t-1)/(t-1) = (t+1)] = 2
==> t=1
On second thoughts, the answer is
D. No values
The above values do not satisfy the equation
Correct answer is D.
cant even solve a simple equation. I wasted a lot of my precious time figuring out the answer.When i was right all the while!!!
dont put up a site with stupid answers like that again…
the correct answer is one
[t^2 -1 / t-1 = (t+1)(t-1)/(t-1) = (t+1)] = 2
==> t=1
and aj it did not satisfy the equation because u have to get it down to the normal form first..
t^2-2t+1=0
now substitute and check it out
Dear dumbass,
We appreciate your comment let see how others react ??
I think the answer must be A. If u put 1 directly into the equation,it gives 0/0, which is indeterminate…We have to bring the equation to a proper form first.
Answer should be D. Anusha, you are right when you say that 0/0 is determinate and thats why there are no values. so the answer is D.
D should be the answer. There is no value which will satisfy this equation.
Take GMAT team, please provide the answer.
Without any doubt answer is D.
How about – B?
(t^2 – 1)/t – 1 = 2 => t^2 – 1=2t-2 => t^2 – 2t + 1 =>
So t=1
Interesting comments on this one
Let me try as well.
(t^2 – 1)/(t-1)=2
Question 1 – can we cross multiply (t-1) i.e. take it to RHS?
NO, unless we know that t-1 is NON-ZERO.
Question 2 – can we divide (t^2 – 1) by (t-1) ?
NO, unless we know that t-1 is NON-ZERO.
Question 3 – Can we bring 2 to LHS? Yes.
[This -subtraction/addition - is the best method for such questions]
The eqn becomes:
(t^2 – 1)/(t-1) – 2 = 0
=> [t^2 - 1 - 2(t-1)] / (t-1) = 0
=> [t^2 - 2t + 1] / (t-1) = 0
For us to be able to solve this eqn. we have to establish two things first:
1) Denominator !=0 and
2) Numerator = 0.
Therefore, t-1 !=0 => t != 1 (t NOT-EQUAL-TO 1)…… (1)
And also, t^2 – 2t + 1 = 0
=> (t-1)^2 = 0
=> t-1 = 0
=> t = 1
BUT, we ‘established’ in (1) that t is not-equal-to 1.
So, we cannot obtain any definite values for t.
Ans should be D.
HTH
~magnus1
D
(t^2 – 1)/(t-1) = 2
if we normalize, we get t = 1, but the overall equation has a pole at t = 1 (in the unit circle), hence this equation shall evaluate to infinity at t = 1, thus this leaves a no solution case…
D
D cannot be any solutrion….jusst substitute the values
D
The answer has to be A i.e 1. The reason being we need to substitute the value when the equation is in normal form. Since in the form equation is in currently, the denominator becomes zero which is incorrect. Hence, normalise the equation and put the answer as 1.
Take GMAT team, can you please give an explanation as to why it is D.
Ans : D
(t^2-1)/(t+1) = (t+1)(t-1)/(t+1) = t+1
So (t+1) = 2
t = 1.
But eqn becomes 0/0 = infinite.
So Ans: D
Ans is A.
we can simply calculate t=1.
and now this is completely different story if we put ‘t-1′ as denominator in any equation will result something ambiguous.
D
ans is A , please post right answers Take GMAT
Nevermind got it
-1 does not work since it does not plug back in the equation
right answer is D