Question

Evaluate the following by using identity-2

Answer 1

$(9 .9) {}^{2} \\ = (10 - 0.1) {}^{2} \\ = (10) {}^{2} + (0.1) {}^{2} - 2 \times 10 \times 0.1 \\ = 100 + 0.01 - 2 \\ = 98.01$

Answer 2

Hy friend, here's ur answer...
(9.9)²
There are two ways to do it...
(i) (a+b)²=a²+b²+2ab
(9+0.9)²= (9)²+(0.9)²+2(9)(0.9)
= 81+0.81+16.2
= 98.01
(ii) (a-b)² = a²+b²-2ab
(10-0.1)²= (10)²+(0.1)²-2(10)(0.1)
= 100+0.01-2
= 98.01

Hope it helped u....