For all integers n, n* = n(n-1). What is the value of x*? 1)

Question

For all integers n, n* = n(n-1). What is the value of x*?

1) x* = x

2) (x-1)* = x - 2

freetheking · Answer

Stmt1.
x(x-1) =x 
x(x-2) = 0 ===> x = 0 or 2 : insuff.(0*=0 but 2*=2)

Stmt2.
(x-1)(x-2) = x-2
(x-2)^2 = 0 ====> x=2 : suff. (2*=2)

Thus, B

MA · Answer

B.
from i, x = 0 or 2.
from ii, x = 2.

Futuristic · Answer

B

From 1:

x* = x
=> x(x-1) = x
If x !=0, then cancel x from both sides, 
x-1=0 or x=1
=>x=0 or x=1 insuff

From 2:
(x-1)* = x-2
=>(x-1)(x-2) = x-2
if (x-2) !=0 
then x-1=1 or x=2.
if (x-2)==0 then x=2. i.e. either way x=2 so 2 is suff

shoonya · Answer

guys, i'm a bit confused here. the way i perceived this question is that we need to calculate x* from a GIVEN X. 


so stimulus (1) should be sufficient.
eg.

x* = x
=> 0* = 0, 1* = 1, 2* = 2.

and stimulus (2) is:

(x - 1)* = (x - 2)

=> (x - 1)* = ((x - 1) - 1)
=> y* = (y - 1)
=> x* = (x - 1)

so, stimulus (2) should be sufficient as well.

It should be D.

laxieqv · Answer

A statement is so-called sufficient when we obtain only one value of the asked parameter ..here the value of the parameter floats with any values of x so the statement is insufficient.

jaynayak · Answer

B

1) 
X* = X
x(x-1) = x
x^2 -2x = 0 
x(x-2) =0
Hence x = 0 or 2 Not suff

2) 
(x-1)* = x-2
(x-1)(x-2) = x-2
x^2 -3x+2 = x-2
x^2 -4x+4 = 0
(x-2)^2 = 0
x=2 Suff

For all integers n, n* = n(n-1). What is the value of x*? 1)

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