I am looking for solution and I really cannot get it right. I was going through some solutions but recently I have just tried to check what would be equation of trendline if the function is simply y=x^2. I have made a table with x increasing 0,5, 10, 15 etc, calculated y correspondingly (0, 25, 100, 225) and excel returns this: y=25,000000000000100x2 - 50,000000000000000x + 25,0000000000218. I presume people in MS know what they do, so how to use that function? I am using Office 365.