For z = x + Iy, let f( z ) = x3+28x2+4y27x2+y2\displaystyle \frac{{{x}^{{3}}+{28}{x}^{{2}}+{4}{y}^{{2}}}}{{{7}{x}^{{2}}+{y}^{{2}}}} where z \displaystyle \ne 0,
limz0f(z)\displaystyle \lim_{{{z}\rightarrow{0}}}{f{{\left({z}\right)}}} =

Use DNE for does not exist, oo for infinity or -oo for negative infinity.