Question

Solve this quadratic equation by completing the square.

x2 + 6x = 18
A. x = -6 + JT8
B. x= -6 + 227
C. x=-3 + 118
D. x = -3 1/27

Answer 1

`x=-3+√(27)\\ x=-3-√(27)`

Explanation:

Let's find our C value for the quadratic equation.

`((6)/(2))^(2) = 9`

That is our C. Since we added 9 to one side, we have to do the same to the other. We get:

`x^(2) +6x + 9 = 18 + 9\\x^(2) +6x + 9 = 27`

Now, lets form the left side as a binomial squared.

`(x+3)^(2) = 27`

Let's square both sides now:

`x+3 = (+/-)√(27)`

Now, we subtract 3 from both sides to isolate the variable, X:

`x= -3(+/-)√(27)`

This means that the answers are:

`x=-3+√(27)\\ x=-3-√(27)`

I do not understand your answers though. Answer A makes no sense, answer B is 221, answer C is 115, and answer D also does not make sense. If you could clarify this portion, maybe I can help you find your alphabetic answer