Question

I don't really get the options on this one I just got 6 (plus or minus) 0 when I worked it out...

Which of the following equations is the result of completing the square on x^2 - 6x - 9 = 0?

a) (x - 3)^2= 0
b) (x - 3^)2= 9
c) (x - 3)^2= 18

Answer 1

Well in order to complete the square...you would add 9 to both sides...

x² -6x = 9

Now take your 'b' value (-6) divide it by 2...and square the result....you add this to both sides of the equation...

so -6/2 = -3...and -3² = 9...so now we have

x² - 6x + 9 = 9 + 9

x² - 6x + 9 = 18

And when you factor the left hand side you get?

Answer 2

So general rules for completing the square...

1) Get into the form * Ax² + Bx = C *
2) Take 'B' and divide it by 2...and square the result...
3) Add that result to both sides of the equation
4) Factor the left hand side

and *although you dont need to here*

5) Take the square root of both sides
6) Solve for 'x'

Answer 3

well to answer the other question 9? but my diddy told me I was wrong

Answer 4

(x - 3)^2= 18

Answer 5

Right ...that is correct...(x - 3)² = 18 is what I get too

Answer 6

yippee! thanks! @johnweldon1993

Answer 7

No problem! :)