Find the square of:

x - 2y + 1

(x - 2y + 1)²

Using the formula

(∵ (x - y + z)² = x² + y² + z² - 2xy - 2yz + 2xz)

= x² + (2y)² + 1² - 2 $\times$ (x) $\times$ (2y) - 2 $\times$ (2y) $\times$ 1 + 2 $\times$ 1 $\times$ (x)

= x² + 4y² + 1 - 4xy - 4y + 2x

Hence,(x - 2y + 1)² = x² + 4y² + 1 - 4xy - 4y + 2x