Find the square of:

3a - 2b - 5c

(3a - 2b - 5c)²

Using the formula

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

= (3a)² + (2b)² + (5c)² - 2 $\times$ (3a) $\times$ (2b) - 2 $\times$ (2b) $\times$ (5c) + 2 $\times$ (5c) $\times$ (3a)

= 9a² + 4b² + 25c² - 12ab + 20bc - 30ca

Hence, (3a - 2b - 5c)² = 9a² + 4b² + 25c² - 12ab + 20bc - 30ca