Question

Find the value of $99\times 101$ using the standard identity.

Answer 1

Compute the required value

Given expression is$99\times 101$

$\Rightarrow 99\times 101=(100–1)\times (100+1)$

We know that $(a+b)\times (a–b)=a^2–b^2$

$\Rightarrow 99\times 101=(100-1)\times (100+1)={\left(100\right)}^2–1^2$

$\Rightarrow 10000–1=9999$

Hence the required value is $9999$