Proportional function: y=kx(k≠0) As long as the values of a pair of x and y or the coordinates of a point are known, k can be obtained after substitution, and then the analytical formula can be obtained. Linear function: y=kx+b(k≠0) As long as the values of two pairs of x and y or the coordinates of two points are known, k and b can be obtained after substitution, and thus the analytical formula can be obtained. Inverse proportional function: y=k/x(k≠0) As long as you know the values of a pair of x and y or the coordinates of a point, you can find k after substitution, and then get the analytical formula. Quadratic function: general form: y=ax? +bx+c(a≠0) needs to know the values of three pairs of x and y or the coordinates of three points. After substitution, a, b and c can be found, and an analytical formula can be obtained. Vertex: y=a(x-h)? +k, (a≠0) If the coordinates of the vertex are (h, k), set an analytical formula with the above formula, and then know the coordinates of a point to determine a. Intersection point: y=a(x-x 1)(x-x2), (a≠0) where x/.