# Math Help - Explain the link

1. ## Explain the link

Can anyone elaborate more about this:

$\sum_{i=1}^n Var(Y_i-\hat{Y}_i)+[E(Y_i-\hat{Y}_i)]^2$=
[Math]\sum_{i=1}^nVar[(Y_i-\overline{Y}-b_1(X_i-\overline{X}))^2][/tex]

How is the 2nd term combine into the variance?

To be more specified: This is the intermediate step in proving [LaTeX ERROR: Convert failed] in regression study. furthermore, [LaTeX ERROR: Convert failed]