Question

Evaluate the following using identities.
${199}^2+199$.

Answer 1

${199}^2+199$

$\Rightarrow 199(199+1)\Rightarrow 199\left(200\right)$

$\Rightarrow (200-1)\left(200\right)$

$\Rightarrow (200{)}^2-200$

$\Rightarrow 40000-200$

$\Rightarrow 39800$.