Calculus
Implicit differentiation
When y is mixed with x — differentiate both sides and solve for dy/dx.
When y is mixed with x in an equation, differentiate both sides treating y as a function of x — then solve for dy/dx.
Try it
x² + y² = 25, find dy/dx
2x + 2y · dy/dx = 0. So dy/dx = −x/y.