Question

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

• A. $74.53$
• B. $73.42$
• C. $79.21$
• D. $73.21$

Answer 1

The correct option is C $79.21$

Given, ${8.9}^2$

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

We know, $(a-b{)}^2=a^2-2ab+b^2$.

Then,

${8.9}^2$

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

$=(9{)}^2-2(9\left)\right(0.1)+(0.1{)}^2$
$=81-1.8+0.01=79.20+0.01=79.21$.

Therefore, option $C$ is correct.