Question

(9.9)^2 by using identity​

Answer 1

Step-by-step explanation:

${9.9}^{2} = {(10 - 0.1)}^{2} = {(10 - \frac{1}{10}) }^{2}$

$= 100 - 2 + \frac{1}{100}$

$= 98 - \frac{1}{100} = \frac{9800 - 1}{100} = \frac{9799}{100}$

$= 97.99$

$≈ 98$

Answer 2

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Question:-

• (9.9)^2 by using identity

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Answer:- 98.01

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Step by step explanation:-

> ( 9.9)^2

> (9+0.9)^2

So ,by using identity

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

Now apply this identity in our question

$⇒ {(9 + 0.9)}^{2} \\ \\ ⇒ {9}^{2} + {0.9}^{2} + 2 \times 9 \times 0.9 \\ \\ ⇒81 + 0.81 + 16.2 \\ \\ ⇒98.01$

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More identities:-

$>{(a - b)}^{2} = {a}^{2} + {b}^{2} - 2ab \\ \\> {a}^{2} - {b}^{2} = (a + b)(a - b) \\ \\> {(a + b)}^{3} = {a}^{3} + {b}^{3} + 3ab(a + b)$

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