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11 votes
11 votes
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User Mitesh Khatri
by
3.4k points

1 Answer

12 votes
12 votes

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}

User Wikimind
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