Question

Using identities, evaluate:
${8.9}^2$

Answer 1

Using the identity ${(a-b)}^2=a^2+b^2-2ab$

${8.9}^2={(9-0.1)}^2$

$=9^2+{0.1}^2-2\times 9\times 0.1$

$=81+0.01-1.8$

$=79.21‬$