Navigate to (or if you've already made a copy, go to your file)[https://docs.google.com/spreadsheets/d/1iAVKV8lji5YKQaSLTc9zMshmKMMFjaGU/copy](https://docs.google.com/spreadsheets/d/1iAVKV8lji5YKQaSLTc9zMshmKMMFjaGU/edit#gid=4287217)

Click "Reinitializing the Independent Variable"

Click in the cell next to the first data point.

We always reinitialize the first data point as either 0 or 1 depending on how we are describing the data. In this case, we are describing the data as years SINCE 1965, so we write 0 to indicate that 1965 is zero years SINCE 1965. Type "0 [[enter]]" 

Click on the cell below the one we just typed in.

Click on the cell with 1974 in it to tell Sheets we will use it in a formula. The name of the cell(A3 in this case) will appear in the cell we were typing in.

We want to answer the question "How many years since 1965 is 1974?" so we will subtract 1974 from 1965.  Type "-"

Click on the cell with 1965 in it to tell Sheets we will use it in a formula. The name of the cell(A2 in this case) will appear in the cell we were typing in.

All of our data will answer the question, "How many years since 1965 is x?" We want the second number in our formula to always refer to the cell with 1965 in it. (A2). This is called an absolute reference. To change A2 into an absolute reference, Type " [[F4]] [[enter]]"

Once we hit enter Sheets does the math 1974-1965 and displays it in the sheet. It will then guess that we want the same formula in all the cells below and suggest that we autofill. Click the check mark to accept the autofill suggestion.

You can click on some of the cells to verify that Sheets is doing what we intended it to do. Cell B4 is subtracting cell A4 from A2 as we intended. Although the cells will always display the answers, we can see how they got to them by clicking on the cells and looking at the formula bar on top.

Cell B6 is subtracting cell A6 from A2 as we intended. Although the cells will always display the answers, we can see how they got to them by clicking on the cells and looking at the formula bar on top.

Cell B7 is subtracting cell A7 from A2 as we intended. Although the cells will always display the answers, we can see how they got to them by clicking on the cells and looking at the formula bar on top.

Cell B8 is subtracting cell A8 from A2 as we intended. Although the cells will always display the answers, we can see how they got to them by clicking on the cells and looking at the formula bar on top.

Cell B10 is subtracting cell A10 from A2 as we intended. Although the cells will always display the answers, we can see how they got to them by clicking on the cells and looking at the formula bar on top.

Now that we have reinitialized the x variables, let's look at our new equation for the line of best fit.

Click here and select the data in Cells B1 to C11

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Now that we have reinitialized the x variables, let's look at our new equation for the line of best fit.