Mathematics
9 Online
OpenStudy (darkbluechocobo):
Help with putting conic equation into vertex form
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OpenStudy (darkbluechocobo):
x2 + 9y2 + 10x − 18y + 25 = 0
OpenStudy (darkbluechocobo):
I know this is an ellipse
OpenStudy (darkbluechocobo):
And it is a horizontal ellipses as well
OpenStudy (anonymous):
complete the square twice
it is a real pain
Nnesha (nnesha):
\[\huge\rm (x^2+10x)+(9y^2-8y)=-25\]
complete the square
left side
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OpenStudy (anonymous):
\[x^2 + 9y^2 + 10x − 18y + 25 = 0 \\
x^2-10x+9y^2-18y=25\] is a start
OpenStudy (darkbluechocobo):
(x^2+10x) + (9y^2-18y)=-25
OpenStudy (anonymous):
x2 + 9y2 + 10x − 18y + 25 = 0
$$x^2+9y^2+10x-18y+25=(x^2+10x+25)+9(y^2+2y+1-1)\\\quad=(x+5)^2+9(y+1)^2-9$$
OpenStudy (anonymous):
factor out the 9 of the y term
\[x^2+10x+9(y^2-2y)=-25\]
OpenStudy (darkbluechocobo):
(x+5)^2+9(y^2-2y)^2=-25
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OpenStudy (anonymous):
er, that should be \(y^2-2y+1-1\) and then \((y-1)^2\)
Nnesha (nnesha):
b/2 = 10/2
take square of 5 add to the right side
OpenStudy (anonymous):
\[(x+5)^2+\overbrace{9(y^2-2y)^2}^{\text{mistake here}}=-25\]
OpenStudy (anonymous):
\[(x-5)^2+9(y-1)^2=-25+5^2+9\]
OpenStudy (darkbluechocobo):
so we are left with (x-5)^2 +9(y-1)^2=9?
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OpenStudy (anonymous):
then divide by 9 to put in standard form
OpenStudy (anonymous):
i made a typo \(-5\) should be \(+5\) of course
Nnesha (nnesha):
it should equal to 1
OpenStudy (darkbluechocobo):
(x+5)^2+(y-1)^2=1
Nnesha (nnesha):
nope
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OpenStudy (anonymous):
divide ALL by 9
Nnesha (nnesha):
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