Question

Using identity evaluate 81 square​

Answer 1

Answer:

(81)2

= (80+1) 2

= (80) 2+2×80×1+(1) 2

[Using, (a+b)

2=a2 +2ab+b2]

= 6400+160+1 = 6561

HOPE IT'S HELPFUL AND PLZ PLZ MARK IT AS BRAINLIST

Answer 2

Answer:

$81 = 80 + 1 \\ 81^{2} = {(80 + 1)}^{2} \\ \\ (80 + 1) ^{2} \: = 80 ^{2} + 2 \times 80 \times 1 + 1 ^{2} \\ \: \: \: \: \: \: \ \: = 6400 + 160 + 1 \\ = 6400 + 161 \\ = 6561$

The answer is 6561