Question

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

• A. $64.81$
• B. $79.21$
• C. $80.21$
• D. $79.51$

Answer 1

The correct option is B $79.21$

${8.9}^2=(8+0.9{)}^2=(8{)}^2+2\times 8\times 0.9+(0.9{)}^2$
$\left[Usingidentity\right(a+b{)}^2=a^2+2ab+b^2]$
$=64+14.4+0.81=79.21$