neetamittal wrote:

There is some flaw in my logic here...pls point it out....

If z┬▓ - 4z > 5 then which of the following is always true

A) z > -5

B) z < 5

C) z > -1

D) z < 1

E) z < -1

I solve it as...

(z - 5) (z +1) > 0

(z - 5) > 0 and (z +1) > 0 => z > 5 and z < -1

OR

(z - 5) < 0 and (z +1) < 0 => z <5 andz>-1So why is the answer E?

Hey Neeta

See the bold part in your analysis..

z+1 > 0 .... so z > -1 ...

z +1 < 0 .... so z < -1 ...

Nuances..thats what get us most of the time

So for the first condition.... z > 5 is always true

and for the second condition.... z <-1 is always true..

i see only z < -1 in the answer choices

The final check :

I would plug two three # 's less than -1 ..like -5 ,-10 , -15...and see whether the inequality holds..

Thanks

Praetorian