9.4.18 Curvilinear integrals

(3) Problem: Calculate the line integrals of the second kind: a) \[ \begin{array}{l} \int_{A B}\left(x^{2}-2 x y\right) d x \\ +\left(2 x y+y^{2}\right) d y \quad \text { where } A B: y \\ =x^{2}, \quad A(1 ; 1), \quad B(2,4), \end{array} \] b) \( \oint_{L}(x-y) d x+(x-y) d y, \quad L: x^{2}+y^{2}=4 \).