Question

evaluate (7.9)² by using the identites ​

Answer 1

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• Evaluate ${(7.9)}^{2}$ using identities.

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• This can be done in two ways.

First Process:-

${(7.9)}^{2}$

$= {(7 + 0.9)}^{2}$

$= {7}^{2} + {(0.9)}^{2} + 2 \times 7 \times 0.9$

$= 49 + 0.81 + 12.6$

$= 62.41$

Second Process:-

${(7.9)}^{2}$

$= {(8 - 0.1)}^{2}$

$= {8}^{2} + {(0.1)}^{2} - 2 \times 8 \times 0.1$

$= 64 + 0.01 - 1.6$

$= 62.41$

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• ${(7.9)}^{2} = 62.41$

$\star\:\:\:\bf\large\underline\blue{Identities\:Used:-}$

• ${(x + y)}^{2} = {x}^{2} + 2xy + {y}^{2}$
• ${(x - y)}^{2} = {x}^{2} - 2xy + {y}^{2}$

Answer 2

Answer:

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