PS question

[poonamchiK]

If a and b are integers and b ≠ 0, whch of the following cannot equal to 0?
a. ab
b. a-b
c. a+b
d. ab-b*2
e. a*2 + b*2 [editor: this appears to be a^2 + b^2, not 2a + 2b]

My answers shortlisted were a and e.
correct answer is e. how come? (a) also could have been the answer!

[nimish.tiwari]

Even if b cannot be zero, 'a' could still be zero. And hence, (a) CAN be Zero. That leaves with (e) as the correct option.

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Nimish.

[ps63739]

I don't find any option correct, is the information in the question correct?

A: a could be zero leading ab = 0.
B: Say a and b both 2 then expression = 0
C: a+b say a = -2 and b = 2 expression = 0
D: Say a = 2, expression = 0
E: Say a = -2, b = 2 expression = 0.

You sure that is all the information we have?

[editor: the problem was mistranscribed; see above.]

[poonamchiK]

Yes thats right... thats abt all the information i have!

bt now i agree with nimish. i understand how we gt answer as e.

Poonam

[ps63739]

I am still not able to get how the answer is E?

Say a = -2 and b = 2, then doesn't that lead to expression as 0?

[poonamchiK]

Very simple now.

a.since b is not equl to zero, a can hence ab=0.
b. and c. give a and be some nos. which can also have it come to zero atleast once
d. give a=b and u will have a zero again.
e. give this any no. including 0 to a. u have the answer! this expression just cannot be zero.

[ps63739]

I believe I assumed * as multiplication sign, however, it seems to be for exponent.

Thanks.

[RonPurewal]

I believe I assumed * as multiplication sign, however, it seems to be for exponent.

Thanks.

yes.

if the last choice is taken to be a^2 + b^2, the answer follows.

-- ron