DS

[yangliu0401]

Is 1/P > R/(R²+2)?

1). P=R
2). R>0

OA is C.

While I choose A.

first, we can dedrive from the inequality above :

1/P > R/(R²+2)=>R²+2>R*P

accoding to 1), the new inequality could be R²+2>R², sufficient
2). not sufficient.

Any comment?

[cramya]

1/P > R/(R²+2)=>R²+2>R*P

The corss multiplication is not allowed since we dont know p,r are negative or positive. If its positive then what u did is ok but we dont know from stm I since all we know is p=r.If its negative the inequality reverses.

This is a trap which we can fall in to when manipulating inequalities.

Q:

Is 1/p > r/r^2+2

Stmt I

p=r

Is 1/r > r/r^2+2

(or) Is 1/r-r/r^2+2 >0

(or) Is r^2+2-r^2/r(r^2+2) > 0

(or) Is 2/ r(r^2+2) > 0

We have no idea if r is positive or negative so INSUFF

Stmt II

r > 0

No idea about p.

INSUFF

Together:


since r>0, 2/ r(r^2+2) > 0 always greater than 0

Choose C

Hope this helps ;let me know if u still hv questions.

Regards,
CR

[yangliu0401]

1/P > R/(R²+2)=>R²+2>R*P

The corss multiplication is not allowed since we dont know p,r are negative or positive. If its positive then what u did is ok but we dont know from stm I since all we know is p=r.If its negative the inequality reverses.

This is a trap which we can fall in to when manipulating inequalities.

Q:

Is 1/p > r/r^2+2

Stmt I

p=r

Is 1/r > r/r^2+2

(or) Is 1/r-r/r^2+2 >0

(or) Is r^2+2-r^2/r(r^2+2) > 0

(or) Is 2/ r(r^2+2) > 0

We have no idea if r is positive or negative so INSUFF

Stmt II

r > 0

No idea about p.

INSUFF

Together:


since r>0, 2/ r(r^2+2) > 0 always greater than 0

Choose C

Hope this helps ;let me know if u still hv questions.

Regards,
CR

woow~~~

[moorthy76]

cool... thanks