Write the expanded form of $$(4a + 9b + 5c)^2.$$​​

Correct option is B

Given :

(4a + 9b + 5c)$$^2$$

Formula used :

$$​(x + y + z)^2 = x^2 + y^2 + z^2 + 2xy + 2xz + 2yz$$

Solution : 

Applying the formula; 

(4a + 9b + 5c)$$^2$$ 

= $$(4a)^2 + (9b)^2 +(5c)^2 + 2\times(4a)\times(9b) + 2\times(9b)\times(5c) + 2\times(5c)\times(4a)$$​​

= $$16 a^2 + 81 b^2 +25c^2 + 2\times(4a)\times(9b) + 2\times(9b)\times(5c) + 2\times(5c)\times(4a)$$

= $$16a^2 + 81b^2 + 25c^2 + 72ab + 90bc + 40ac$$

The correct answer is option (b) $$16a^2 + 81b^2 + 25c^2 + 72ab + 90bc+ 40ac$$.