I am currently learning how to work with Cauchy-Riemann equations. The equation is f(z) = 2x+ixy^2. My question: is u(x,y) = 2x or just x? At this link: http://www.math.mun.ca/~mkondra/coan/as3a.pdf in letter e) they say u(x,y) is equal to x. But I don't understand how that is possible. Is that a typo or am I missing something critically important? Thank you.