Creeper300 wrote:

ab = 0?

(1) a + b + ab = 0

(2) a - b = 0

Is ab = 0?

implies Is either a or b or both = 0? i.e. is it necessary that at least one of them has to be 0?

(1) a + b + ab = 0

a(1+b) = -b

a = -b/(1+b)

If b = 0, a = 0

If b = 1, a = -1/2

So ab may or may not be 0. Not sufficient.

(2) a - b = 0

a = b

If a = 0, b = 0

If a = 5, b = 5

So ab may or may not be 0. Not sufficient.

Using both, a + a + a^2 = 0

2a + a^2 = 0

a(2+a) = 0

So either a = 0 (so b = 0) or a = -2 (so b = -2)

In first case, ab = 0. In second case ab = 4.

So ab may or may not be 0. Not sufficient.

Answer (E)

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