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Hello! I am working on the Modeling Project #1 still and I am having such issues with the data sets for the rest of the worksheet. I keep reading and I see that your doing grade average versus percentage of assignments, but I am confused on what it is asking or what method I am supposed to be using. I got the first question, solving for a, b, and c and I am familiar with the quadratic forumla, I am just missing something on how to start these next two problems.
Could you give me a boost to what to do?
What that boils down to can be summarized by a table.
For example, consider the following
x y
2 20
5 50
12 130
From this table and the form y = a x^2 + b x + c you get the equations
20 = 4 a + 2 b + c
50 = 25 a + 5 b + c
130 = 144 a + 12 b + c
which you can solve by elimination, as you did with the first question.
Now you are given data for grade ave. vs. percent of review. You could make a table of y vs. x, with y the grade average and x the percent of review. You could replace the heading 'x' in the first column with the identifier 'percent of review' and the 'y' in the second column with 'grade ave', so your table would represent percent of review vs. grade average.
Your table would have several additional rows (one additional row for every 'data point'). You are instructed to choose three data points, and to base your model on those three points. You could for example make a 'shortened table' with just the three points you choose, very similar to the table given above (but with different numbers). To get a quadratic model you would again use the form y = a x^2 + b x + c to get three equations, one for each point. Solving the equations for a, b and c and plugging those values back into the form y = a x^2 + b x + c gives you your model.
Let me know if this doesn't help.