The complex number $\large\frac{1+2i}{1-i}$ lies in which quadrant?

$\large\frac{1+2i}{1-i}=\frac{1+2i}{1-i}\times\frac{1+i}{1+i}$
$=\large\frac{1-2+3i}{2}=\frac{-1+3i}{2}$