Help with Polynomial Equation

If this is a rare or one time thing, simply hand enter the coefficients of the polynomial into 4 convenient cells in the spreadsheet. Then build a suitable formula in C19 and copy it down. This could be =cell1*B19^3+cell2*B19^2+cell3*B19+cell4. With a cubic polynomial or higher, I often use the SERIESSUM() function =cell4+SERIESSUM(B19,1,1,cell1:cell3) https://support.office.com/en-us/art...4-96c49087f637 Be sure to format the formula text in the chart to display all significant figures to avoid errors from too few sig figs in some of those terms. Also, pay careful attention to relative and absolue references so the formula will be easy to copy.

If this is something you will do frequently, I would suggest you learn how to perform these polynomial regressions using the LINEST() function. There is an example of entering the LINEST() function for a cubic polynomial in the help file (just before the examples start): https://support.office.com/en-us/art...a-fa7abf772b6d

Because "linear" in linear regression means "linear in its solved coefficients," which polynomials are.

It's not more clever; LINEST just sees multiple x variables, unaware that they are powers of a single variable.