Question

Find the following product by using suitable identity

$(7.16\times 7.16+2.16\times 7.16+2.16\times 2.16)$

• A. $64.4567$
• B. $25.6458$
• C. $71.3968$
• D. $53.6458$

Answer 1

The correct option is C $71.3968$

$Letx=7.16andy=2.16Therefore,x^2+y^2+xy=x^2+y^2+xy+xy-xy={(x+y)}^2-xy={(7.16+2.16)}^2-7.16\times 2.16={\left(9.32\right)}^2-15.4656=86.8624-15.4656=71.3968$

Hence, option (C) is the correct answer.