The step required to solve the given equation by completing the squares is required.
The required step is [tex](x-4)^2=23[/tex]
The equation is
[tex]x^2-8x-7=0\\\Rightarrow x^2-8x=7[/tex]
Here
[tex]b=-8[/tex]
[tex]\left(\dfrac{b}{2}\right)^2=\left(\dfrac{-8}{2}\right)^2=16[/tex]
Adding the above expression to the equation on both sides
[tex]x^2-8x+16=7+16[/tex]
[tex]\Rightarrow x^2-4x-4x+16=23[/tex]
[tex]\Rightarrow (x-4)^2=23[/tex]
[tex]\Rightarrow x-4=\pm\sqrt{23}[/tex]
[tex]\Rightarrow x=4+\sqrt{23},4-\sqrt{23}[/tex]
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