Answer:
36 cm²
Step-by-step explanation:
Add the bases, then multiply by the height
So it's
(2 + 4) 6
6 • 6
36 cm²
Answer:
19
Step-by-step explanation
Let the sum of n terms of A.P. = Sn
The answer is

. I've demonstrated the 'split and combine' method in the image attached.
This principal is based on the fact that you can multiply and divide radicals as you would with regular integers, but you remember that the answers remain as radicals unless the number you're dealing with is a square (e.g. 9, 16, 25).