Use Euler's method with step size $0.25$ to compute the approximate $y$-values $y_1,$ $y_2,$ $y_3,$ and $y_4$ of the solution of the initial-value problem $$y' = -1 - 4 x + 2 y, \ \ \ y(1)=0.$$
$y_1=$ ,
$y_2=$ ,
$y_3=$ ,
$y_4=$ .