Use Euler's method with step size $0.5$ to compute the approximate $y$-values $y_1,$ $y_2,$ $y_3,$ and $y_4$ of the solution of the initial-value problem $$y' = y - 2 x, \quad y(1)=0.$$

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1. $y_1 =$ 2. $y_2 =$ 3. $y_3 =$ 4. $y_4 =$

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