Question 970776
If you are using a calculator such as a TI83,TI84,etc, then


Step 1) Hit the STAT key and go to "edit". You'll see lists L1,L2,L3...


Step 2) Type the x coordinates of each point into list L1. So you are typing in 1,3,6 into list L1. The first column.


Step 3) Type the y coordinates of each point into list L2. So you are typing in 2,4,-8 into list L2. The second column.


Step 4) Hit the STAT key and scroll to the right once to get to the "Calc" menu. Then scroll down to "QuadReg". That stands for "Quadratic Regression". Hit enter twice to have the calculator compute the three coefficients a,b,c


Step 5) The calculator will report: a = -1, b = 5, c = -2


Any quadratic is in the form {{{ax^2 + bx + c}}}


So the quadratic that goes through the three points (1,2), (3,4), (6, -8) is {{{red(-x^2 + 5x - 2)}}}