If x varies as y, then which of the following is/are correct?<br>1. x^{2}+y^{2} varies as x^{2}-y^{2}<br>2. \frac{x}{y^{2}} varies inversely as y<br>3. \sqrt[n]{x^{2}y} varies as \sqrt[2n]{x^{4}y^{2}}<br>Select the correct answer using the code given below:

  1. A. 1 and 2 only
  2. B. 2 and 3 only
  3. C. 3 only
  4. D. 1, 2 and 3

Correct Answer: D. 1, 2 and 3

Explanation

Given x = ky. Stmt 1: x^2+y^2 = y^2(k^2+1) and x^2-y^2 = y^2(k^2-1), since their ratio is constant, they vary directly (True). Stmt 2: \frac{x}{y^2} = \frac{ky}{y^2} = \frac{k}{y}, which is inverse variation with y (True). Stmt 3: \sqrt[2n]{x^4y^2} = \sqrt[n]{x^2y}, so it varies as itself, making it trivially proportional (True).

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