Answer: 7x+5 is the length of one side
Explanation:
Note: a square's area = x^2
Procedure: We need to factor 49x^2+70x+25 to (x+c)^2
49x^2+70x+25 = (7x)^2 + 2(5)(7) + (5)^2
= (7x+5)^2
Since, area of square = x^2
and, length of one side = x
therefore, x^2 = (7x+5)^2
x = 7x+5