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Finding Square of a Number Using Identity

Question 6vii...

Question

Question 6(vii)
Using identities, evaluate:
$78 \times 82$

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Solution

$78 \times 82 = (80 - 2) \times (80 + 2) = (80)^{2} - (2)^{2}$
$[U s i n g i d e n t i t y (a - b) (a + b) = a^{2} - b^{2}]$
$= 6400 - 4 = 6396$

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Finding Square of a Number Using Identity

Standard VIII Mathematics

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