(iii) xy – x – y + 1 = 0
(iv) xy – y² – x + y = 0

Solution:

(iii) xy – x – y + 1 = 0

We will replace the value of x by x + 1 and y by y + 1

Then,

(x + 1) (y + 1) – (x + 1) – (y + 1) + 1 = 0

xy + x + y + 1 – x – 1 – y – 1 + 1 = 0

Simplifying further we get,

xy = 0

∴ The transformed equation is xy = 0.

(iv) xy – y² – x + y = 0

We will first replace the value of x by x + 1 and y by y + 1

Then,

(x + 1) (y + 1) – (y + 1)² – (x + 1) + (y + 1) = 0

xy + x + y + 1 – y² – 1 – 2y – x – 1 + y + 1 = 0

Simplifying further we get,

xy – y² = 0

∴ The transformed equation is xy – y² = 0.