In physics lab course I measured equivalence conductivity of NaCl in infinite dilution Λ0 as a function of temperature T. So I have observations (T, Λ0) and fitted a line using the least squares method in Ms excel (lol ). The formula of the line is Λ0(T)=c0+c1T, where c0 and c1 are constants. I am asked to estimate the error of Λ0(25 C) using the following formula σΛ0(T)=(C11+T(C12+C21)+T2C22), where Cij are elements of covariance matrix and T is temperature in centigrades. I have matlab, but don't know the commands and how to calculate. I am also asked to derive the formula above on paper and honestly I have no idea where to begin. However, I am given this clue; Those partial derivatives confuse me I will appreciate any help!