Question

How many natural numbers lie between 20² and 21²​

Answer 1

Answer:

41

Step-by-step explanation:

20 square 400

21 square 441

Answer 2

Answer:

$naturnal \: number \: lies \: bewteen \: {20}^{2} \\ and \: {21}^{2} \\ = different \: bewteen \: \\ {21}^{2} \: and \: {20}^{2} \\ {21}^{2} - {20}^{2} = (21 - 20)(21 + 20) \\ 41$

${(a + b)}^{2} = {a}^{2} + 2ab + {b}^{2} \\ {(a - b)}^{2} = {a}^{2} - 2ab + {b}^{2} \\ {a}^{2} - {b}^{2} = (a + b)(a - b)$