Respuesta :

Step 1

Given;

Step 2

[tex]\begin{gathered} Half\text{ of the coefficent of x=}\frac{-8}{2}=-4 \\ Add\text{ \lparen-4\rparen}^2\text{ to both sides} \\ x^2-8x+(-4)^2=20+(-4)^2 \\ x^2-8x+16=36 \\ (x-4)^2=36 \end{gathered}[/tex]

Answer;

[tex]16[/tex]

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