Find the value of the following using $(x + a) (x + b) = x^{2} + (a + b) + a b$
$7.1 \times 7.3$

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Solution

We have,
$7.1 \times 7.3$
$(7 + 0.1) (7 + 0.3)$

We know that
$(x + a) (x + b) = x^{2} + (a + b) x + a b$

Therefore,
$\Rightarrow 7^{2} + (0.1 + 0.3) 7 + 0.1 \times 0.3$
$\Rightarrow 49 + (0.4) 7 + 0.03$
$\Rightarrow 49 + 2.8 + 0.03$
$\Rightarrow 51.83$

Hence, this is the answer.

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