Final answer:
To find an expression for y in terms of k and x, we can set up the given ratio equation and solve for y to get y = -x(1 + k) / (1 - k).
Step-by-step explanation:
To find an expression for y in terms of k and x, we can set up the given ratio equation: (y + x) : (y - x) = k : 1.
Cross multiplying, we get (y + x) = k(y - x).
Distributing, we get y + x = ky - kx.
Combine like terms, we get y - ky = - x - kx.
Factor out y on the left side, we get y(1 - k) = -x(1 + k).
Finally, solving for y, we divide both sides by (1 - k) to get y = -x(1 + k) / (1 - k).