Bunuel wrote:

Does (x + a)^2 = y^2?

(1) x = y - a

(2) x = y + a

Kudos for a correct solution.

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of VA(Variable Approach) method is modifying the original condition and the question, and rechecking the number of variables and the number of equations.

We can modify the original condition and question as follows.

\((x + a)^2 = y^2\)

\(⇔ (x + a)^2 - y^2 = 0\)

\(⇔ (x + a + y )(x+a-y) = 0\)

\(⇔ x = -y - a\) or \(x = y - a\)

Therefore, the condition 1) only is sufficient.

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