help with completing the square
- Thread starter Rani
- Start date
X^2 + 11x + 21/4 = 0
move 21/4 to the right of the equal sign
X^2 + 11x = 0 - 21/4
take half of 11 and replace the third term with the square of half the second and add it to -21/4 since the 11x is positive
11/2
(11/2)^2
X^2 + 11x + 121/4 = -21/4 + 121/4
convert the first term and the half of the second to squared form
(x + 11/2)^2 = 25
Take the square root of the right and the left leaving:
x + 11/2 = ± 5
x = -11/2 ± 5
x = -11/2 + 10/2 x = -11/2 - 10/2
x = -1/2 x = -21/2
Edited this post. Hope I did this right...lol
Can someone else verify this is correct?
move 21/4 to the right of the equal sign
X^2 + 11x = 0 - 21/4
take half of 11 and replace the third term with the square of half the second and add it to -21/4 since the 11x is positive
11/2
(11/2)^2
X^2 + 11x + 121/4 = -21/4 + 121/4
convert the first term and the half of the second to squared form
(x + 11/2)^2 = 25
Take the square root of the right and the left leaving:
x + 11/2 = ± 5
x = -11/2 ± 5
x = -11/2 + 10/2 x = -11/2 - 10/2
x = -1/2 x = -21/2
Edited this post. Hope I did this right...lol
Can someone else verify this is correct?
Last edited:
Thank you for correcting my post JeffM! I knew I kinda remembered how to do this but wasn't exactly sure. You helped me to remember why this actually works and how to handle the slightly more complex forms of completing the square. I really appreciate your response.