Definition of integration

Integration is the opposite of differentiation.

Instead of finding the gradient function - f'(x) or \frac{dy}{dx} - from the normal function, we instead find the normal function, given the gradient function.

Integral notation

We can write the integral of a function y like this:

\int y\space dx

For example, for the function 2x^2-4x+1:

\int 2x^2-4x+1\space dx

This means “the integral of y with respect to x”.