Answer:
27
Explanation:
Since it is addition to make the expression a perfect square, it would not be as direct
√9577 = 97.86214794
we round off to the nearest whole number, since we need a perfect square number
therefore it would be 98
98² = 9604, the perfect square number we'll get after adding to 9577
therefore amount needed to add= 9604-9577= 27