Machine-translated by Google. Questions are authored in English.
Top

Discussion

If two distinct non-zero real variables x and y are such that (x + y) is proportional to (x − y) then the value of \(\dfrac{x}{y}\)

  • A.depends on \(xy\)
  • B.depends only on \(x\) and not on \(y\)
  • C.depends only on \(y\) and not on \(x\)
  • D.is a constant

Answer: D

The ratio \(x/y\) is a constant.

Proportionality means \(x + y = k(x - y)\) for some fixed constant k. Collect the terms:

\[ \begin{aligned} x + y &= kx - ky \\ y(1 + k) &= x(k - 1) \\ \frac{x}{y} &= \frac{k + 1}{k - 1} \end{aligned} \]

The right-hand side contains only the constant k, so \(x/y\) takes the same value whatever the individual values of x and y (and \(k \neq 1\), since y is non-zero). It therefore does not depend on \(xy\), on x alone or on y alone.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.