Answer:
A, B, C are perfect squares. Their roots are 22, 66, 89.
D is not a perfect square. The root is about 94.995
Step-by-step explanation:
Your calculator can help. The integer is a perfect square if its square root is an integer.
A. √484 = 22 . . . . 484 is a perfect square
B. √4356 = 66 . . . . 4356 is a perfect square
C. √7921 = 89 . . . . 7921 is a perfect square
D. √9024 ≈ 94.9947... . . . . not a perfect square
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Additional comment
When you compute the square root using the "long division" method, the first step is to divide the radicand into groups of 2 digits. The most significant digit of the root will be the root of the largest square less than the leftmost group.
For example, the first step in finding the root of 4356 is to divide it into the groups 43'56'. The most significant digit of the root will be 6, because 36 = 6² is the largest square less than or equal to 43.
If the number is a perfect square, the least-significant digit of the radicand will be the least-significant digit of the square of the least-significant digit of the root. Here, the least digit of 43'56' is 6, which can only be the least-significant digit of 4² = 16 or 6² = 36. No other single digits have a square ending in 6.
So, if the number 4356 is a perfect square, it must be the square of 64 or 66. It is the square of 66. (If you're familiar with powers of 2, you know 64²=4096.)
