Find the square of:

2x - 3y + z

(2x - 3y + z)²

Using the formula

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

= (2x)² + (3y)² + (z)² - 2 $\times$ (2x) $\times$ (3y) - 2 $\times$ (3y) $\times$ (z) + 2 $\times$ (z) $\times$ (2x)

= 4x² + 9y² + z² - 12xy - 6yz + 4xz

Hence, (2x - 3y + z)² = 4x² + 9y² + z² - 12xy - 6yz + 4xz