Bunuel wrote:

If a square region has area x, what is the length of its diagonal in terms of x?

(A) √x

(B) √(2x)

(C) 2√x

(D) x√2

(E) 2x

Because \(s^2\) = area of a square:

\(s^2 = x\)

\(s = \sqrt{x}\)

A square's diagonal* is given by \(s\sqrt{2}\)

\(\sqrt{x} * \sqrt{2} = \sqrt{2x}\)

Answer B

*OR use Pythagorean theorem, where hypotenuse = diagonal = d

\((\sqrt{x})^2 + (\sqrt{x})^2 = d^2\)

\(2x = d^2\)

\(\sqrt{2x} = \sqrt{d^2}\)

\(d =\sqrt{2x}\)

_________________

In the depths of winter, I finally learned

that within me there lay an invincible summer.

-- Albert Camus, "Return to Tipasa"