Note that the difference Δ y and Δ y are increments of the function. When the function is differentiable, δy =δx+a(x), where a is constant and a(x) is δ x->; 0 is an infinitesimal quantity higher than Δ x, and the differential dy = Δ x = Δ dx. Generally, dy ≠ δ y.

Introduction to advanced mathematics;

Higher mathematics refers to a more complicated part of mathematical objects and methods compared with elementary mathematics and secondary mathematics. Algebra, geometry and simple set theory in middle schools are called secondary mathematics, which is regarded as the transition between elementary mathematics in primary and secondary schools and advanced mathematics in universities.

Generally speaking, advanced mathematics is a basic subject formed by calculus, algebra, geometry and their intersection. The main contents include: series, limit, calculus, spatial analytic geometry and linear algebra, series, ordinary differential equations. Basic subjects for postgraduate examinations in engineering, science and engineering and finance.