If |a + 1| =|b - 1|, what is the value of a - b? (1) ab 0 (2) a/b-1

Question

If  |a+1|=|b-1| , what is the value of  a-b  ?

(1)  ab>0

(2)  \frac{a}{b}≠ -1

stne · Answer

|a+1|=|b-1|

This eqn only holds for certain combinations of  a  and  b  
 
i.e. if  a=4  then  b  has to be either  6  or  -4

So  a-b  can be either  -2  or  8

If  a=-6  then  b  can be  6  or  -4

So  a-b=-12  or  -2

Similarly we can verify by taking other numbers too

(1)  ab>0

This implies  a  and  b  have to have the same sign

So if  a  is  4   then  b  has to be  6  and  a-b=-2

If  a=-6  then  b  has to be  -4  and  a-b=-2

(other values for a and b will give similar result)

SUFF.

(2)  \frac{a}{b}≠ -1

Again from our pre-work we can see that we cannot have  a=4  and  b=-4  nor can we have  a=-6  and  b=6

Thus the only other possibility is  a=4  and  b=6  or  a=-6  and  b=-4

Thus  a-b=-2

(other values for a and b will give similar result)

SUFF.

Ans D

Hope it helps.

Bunuel · Answer

RiyaGangar · Answer

But in statement 2, a and b can be 0 right?

stne · Answer

No, that is not possible.

0 divided by 0 is undefined.

If |a + 1| =|b - 1|, what is the value of a - b? (1) ab > 0 (2) a/b-1