Guide 4 Chap 10 page 168

[kpkanupriyakhmi]

Q5:-
if|a+b|-c<d, which of the following must be true?
A) a+b>0
B)d>c whenever c<0
C) d+c>0

[n00bpron00bpron00b]

|a+b| - c < d ; which must be true

a) a + b > 0

This need not be true ; remember any value inside the mod is always positive ; but it can also be "0"

Minimum mod value is 0

So, the actual value of a+b is >= 0 ; condition fails

b) d>0 whenever c<0

|a+b| - c < d

we know one thing for sure ; the value of |a+b| is either 0 or some positive value.

Consider the value of |a+b| = 0
c<0 ; if c = -1

0 - (-1) < d
1 < d

In general for any value of |a+b| and any negative value of "c" ; d will always be greater than 0 ; because of the double negative

So condition (B) is true

c) d+c > 0

|a+b|-c < d
|a+b| < d + c
|a+b| = value could be either 0 or any positive value

if |a+b| = 0
0 < d + c (satisfies)

So condition (c) is true

Ans. (B), (C)

[tommywallach]

Great explanation from Noob!

-t

[kpkanupriyakhmi]

One more Q I am solving manhattan 5lb these days. What should be the time limit for each Q in V as well as in Q?

[tommywallach]

Hey KP,

This question doesn't belong in this thread, but in the general Q's thread. Please post it there. Thanks!

-t