jsphcal wrote:

MacFauz wrote:

jsphcal wrote:

Does ab = a^2

(1) a^2 = b ^2

(2) a^3 = b ^3

1) a = + or - b. If a = +b. Answer is yes. If a = -b. Answer is no. Insufficient.

2)a = b. Sufficient.

Answer is B.

MacFauz

thanks for the reply, could you please elaborate more on the algebra use to solve?

(1) and why if a= + or -b or if a = +b stmt 1 suff, and if a = -b then insuff

did you pick numbers to test stmt 1 and 2?

1. We do not need to pick numbers.

1) \(a^2 = b^2\)

This means + or - a = + or - b. So we are basically given that a can be equal to b or a can be equal to -b.

If a = b, LHS of given equation becomes a^2 and hence is equal to RHS

If a = -b, LHS of given equation becomes -a^2 and hence may not be equal to RHS.

Since we are getting two different answers, this statement is insufficient.

2) \(a^3 = b^3\)

This means a = b and nothing else.

So, LHS of given equation can only be a^2 and hence is equal to RHS. Sufficient.

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