Question

Find the value of the following using $(x+a)(x+b)=x^2+(a+b)+ab$
$102\times 99$

Answer 1

We have,

$102\times 99$

$(100+2)(100-1)$

We know that

$(x+a)(x+b)=x^2+(a+b)x+ab$

Therefore,

$\Rightarrow {100}^2+(2-1)100-2\times 1$

$\Rightarrow 10000+100-2$

$\Rightarrow 10098$

Hence, this is the answer.