Could you help me with this question please?

. In regression model yi, = ,3.) + 131:; + En {a} prove that the sum of the Y observations is thehsame as the sum of the t ted 1values in regression model ya. = .30 + .3111: + Ei- That i3 21': = ZYI- {h} prove that the sum of the residuals weighted by the tted values is zero. That is Z ea = ID