Question

using the prime factorisation method, find which of the following number are not perfect square 400​

Answer 1

Answer:

the prime factors of each of the numbers as follows :

400 = 2 × 2 × 2 × 2× 5 × 5 = 2⁴ × 5²

The prime factors have even powers hence 400 is a perfect square.

Answer 2

Answer

400=40×10

=(5×8)×(2×5)

=(5×2×2×2)×(2×5)

Here 5 , 2 ,and 2 make pair of 2

Therefore,√400=√5×2×2×2×2×5

√400=5×2×2

√400=20

20 is square root of 400