y = -9E-05x2 + 0.0061x + 0.769

This is a polynomial trendline shown in Excel. What does -9E-05x2 mean in mathmatical terms? As it's 2nd-order polynomail, x2 should be x square. E-05 is waht? From the resulting y given a specified x, E-05 cannot be exp(-5). Does nayone have the same problem understanding what Excel mean in trendline equations? Thanks.

You can put -9E-05 in a cell and change the number format from Scientific to Number. Or, simply look in the formula bar.

Another trick is to select the label containing the formula and change its format. I do this when I want more precision (more significant figures) for a curve fit.

-9e-05 is the way computers display scientific notation, where -9 is the mantissa and -05 is the exponent (E stands for exponent). So this is -9*10^-5.

If you are trying to copy trendline coefficients to a worksheet cell in order to calculate values along that trendline, note that those coefficients are rounded to the specified number of digits. If you use those coefficients exactly as displayed, there's a good chance you'll get garbage. Make sure you increase the number of displayed digits, so you get better precision. Or use LINEST to obtain the coefficients to Excel's full 15 digit limit.