Answer:
length of side = 10x + 3
Step-by-step explanation:
The area of a square = s² ( s is the length of the side )
given
A = 100x² + 60x + 9 ← perfect square in the form
(a + b)² = a² + 2ab + b²
100x² = (10x)² ⇒ a = 10x
9 = 3² ⇒ b = 3
and 2ab = 2 × 10x × 3 = 60x, hence
100x² + 60x + 9 = (10x + 3)²
s = = 10x + 3 ← length of side