I

${\left(1\frac{1}{2}\right)}^2={\left(\frac{3}{2}\right)}^2=\left(\frac{9}{4}\right)=2\frac{1}{4}$

${\left(1\frac{1}{2}\right)}^2={\left(1+\frac{1}{2}\right)}^2=1^2+2\cdot 1\cdot \frac{1}{2}+{\left(\frac{1}{2}\right)}^2=1+1+\frac{1}{4}=2\frac{1}{4}$