Single layer machine learning is actually linear equation. Linear equation is at most multi-variant polynomial equation, which at most include multiplication and adding.
Deep learning uses multi layers. The multi layers is considered to be non-linear equation. Non-linear equation may include sin, cos, square etc on variances.
Both linear and non-linear equation fits curvature. However, non-linear is more flexible. Below are the equations for linear and non-linear ones.
Linear equations:
Non-linear equations:
