If $a + b = 7$ and $a b = 10$ ; find $a - b$

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Solution

The correct option is A $\pm 3$
Given,
$a + b = 7, a b = 10$
$(a + b)^{2} - (a - b)^{2} = 4 a b$
$=> 7^{2} - (a - b)^{2} = 4 \times 10$
$=> 49 - (a - b)^{2} = 40$
$=> (a - b)^{2} = 49 - 40$
$=> (a - b)^{2} = 9$
$=> a - b = \sqrt{3}$
$=> a - b = \pm 3$

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(a^{2} - a b + b^{2})

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