Answer:
49 + 56k + 16 k^2
Step-by-step explanation:
The area of a square is found by
A = s^2 where s is the side length
A = ( 7 + 4k) ^2
We can use ( a+ b) ^2 = a^2 + 2ab + b^2 where a = 7 and b = 4k
A = 7^2 + 2 * 7 * 4k + ( 4k) ^2
= 49 + 56k + 16 k^2
