Question

(9.9)² using identities

Answer 1

9.9 can also be written as( 10-0.1)
(9.9)² = (10-0.1)²
using the formula: (a-b)² = a²+ b² -2ab
(10-0.1)² = 100+0.01- 2(2*10*0.1)
= 98.01

Answer 2

Given:

(9.9)²

To find:

The solution of (9.9)² using identities.

Solution:

To solve this, first of all, we should know about one of the algebraic identities which is

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

So, proceeding to the solution, we have,

${9.9}^{2}$

This can be written as

${(10 - 0.1)}^{2}$

$= {10}^{2} + {0.1}^{2} - 2(10)(0.1)$

(using algebraic identity mentioned above)

On solving, we get,

$= 100 + 0.01 - 2$

$= 100.01 - 2$

$= 98.01$

Hence, the value of (9.9)² is 98.10