To find the equation of a quadratic function given 3 points, you can use the following steps:
1. Write the general form of a quadratic function: y = ax^2 + bx + c
2. Plug in the coordinates of the first point to get an equation: y1 = a(x1)^2 + b(x1) + c
3. Plug in the coordinates of the second point to get another equation: y2 = a(x2)^2 + b(x2) + c
4. Plug in the coordinates of the third point to get a third equation: y3 = a(x3)^2 + b(x3) + c
5. Use a system of equations to solve for a, b, and c. You can do this by either substitution or elimination.
Once you have solved for a, b, and c, you can plug them back into the general form of the quadratic function to get the equation.