SOLUTION: Find the equation of the ellipse center: C(-2,3) major axis is horizontal passes through (1,4) (2,3)

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Question 1042211: Find the equation of the ellipse
center: C(-2,3)
major axis is horizontal
passes through (1,4) (2,3)

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
Find the equation of the ellipse
center: C(-2,3)
major axis is horizontal
passes through (1,4) (2,3)

----------------------

So that I won't be doing your homework for you, 
I'll do one exactly like yours with the numbers
changed but with the same step-by-step procedure:

Find the equation of the ellipse 
center: C(-3,4) 
major axis is horizontal
passes through (1,5) (2,4)

All ellipses with center (h,k), semi-major axis length
"a", and semi-minor axis length "b", has equation: 

%28x-h%5E%22%22%29%5E2%2Fa%5E2%2B%28y-k%5E%22%22%29%5E2%2Fb%5E2%22%22=%22%221

Since we know that the center is C(-3,4), we know that
(h,k) = (-3,4), so we can substitute -3 for h and 4 for k.

%28x-%28-3%29%5E%22%22%29%5E2%2Fa%5E2%2B%28y-4%5E%22%22%29%5E2%2Fb%5E2%22%22=%22%221

or

%28x%2B3%29%5E2%2Fa%5E2%2B%28y-4%29%5E2%2Fb%5E2%22%22=%22%221

We plot the given points. And since the major axis is 
horizontal and the point (2,4) has the same y-coordinate 
as the center, that means that the point (2,4) is the 
right vertex of the ellipse.  So we can sketch it in
like this:



Let's draw in the semi-major axis (in green):



By counting the blocks on the graph paper, we know
that the major axis is 5 units long.  And since "a"
is the length of the major axis, we can substitute 5
for "a" in the equation:

%28x%2B3%29%5E2%2Fa%5E2%2B%28y-4%29%5E2%2Fb%5E2%22%22=%22%221

and now we have the equation 

%28x%2B3%29%5E2%2F5%5E2%2B%28y-4%29%5E2%2Fb%5E2%22%22=%22%221

or squaring 5:

%28x%2B3%29%5E2%2F25%5E%22%22%2B%28y-4%29%5E2%2Fb%5E2%22%22=%22%221

All we have left is to find the value of "bē".

To get that we use the point (1,5) that the ellipse
passes through.  We know that when x=1 and y=5, the
equation must be true, so we substitute those
temporarily for the variables x and y:

%28x%2B3%29%5E2%2F25%5E%22%22%2B%28y-4%29%5E2%2Fb%5E2%22%22=%22%221

%281%2B3%29%5E2%2F25%5E%22%22%2B%285-4%29%5E2%2Fb%5E2%22%22=%22%221

%284%29%5E2%2F25%5E%22%22%2B%281%29%5E2%2Fb%5E2%22%22=%22%221

16%2F25%5E%22%22%2B1%2Fb%5E2%22%22=%22%221

We multiply through by the LCD of 25bē

16b%5E2%2B25%22%22=%22%2225b%5E2

Subtract 16bē from both sides:

25%22%22=%22%229b%5E2

Divide both sides by 9

25%2F9%22%22=%22%22b%5E2

Now we can substitute that for bē and we have the
complete equation for the ellipse:

%28x%2B3%29%5E2%2F25%5E%22%22%2B%28y-4%29%5E2%2F%2825%2F9%29%22%22=%22%221

Now all you have to do is use the above as a model
and do yours step-by-step as the above.

Edwin