Answer:
9 m
Explanation:
If x is the length of the original square, then x+5 is the length of the new square.
Area of a square is the square of the side length, A = s². Since the area of the new square is 196 m²:
196 = (x + 5)²
Solving, first take the square root of both sides:
±14 = x + 5
Subtract 5 from both sides:
x = -5 ± 14
x = -19, x = 9
x can't be negative, so x = 9. The side length of the original backyard is 9 m.