One is to find analytic function (curve equation) from point coordinates, basic quantity of function and other conditions. There are several unknowns in the function (curve), and several equations are needed to determine the analytical formula.

The second is to know the analytical formula of function (curve equation) and find the basic quantity, image and image properties of function (curve).

The core of function (curve, the same below) is analytical formula (equation, the same below) and image. The image properties of a function include three image properties: the domain and value domain of the function, symmetry (including parity), monotonicity and extremum.

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