Question

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Answer 1

We need to solve the following equation by completing the square:

$x^2-4x-9=0$

we first pass the 9 to sum in the right side

$x^2-4x=9$

now we add 4 in both sides of the equation, because (4/2)^2=4, obtaining

$x^2-4x+4=9+4$

simplifying

$(x-2)^2=13$

then

$(x-2)=\pm\sqrt[]{13}$

adding 2 in both sides of the equation we have that the solution is:

$x=2\pm\sqrt[]{13}$