Question 750027:  find the equation of the ellipse given center @(0,0) and the major axis parallel to x-axis  distance between foci 4/3squareroot of 33, passing through (2,1) 
 Answer by josgarithmetic(39630)      (Show Source): 
You can  put this solution on YOUR website! "distance between foci 4/3squareroot of 33"---- 
That means the foci are (-(2/3)sqrt(33),0) and ((2/3)sqrt(33),0).  Use the distance formula to make the expression for the sum of the distances (-(2/3)sqrt(33),0) to (2,1) and ((2/3)sqrt(33),0) to (2,1).  That sum will be equal to 2*a, so you will be able to get a value for a.  
 
 
 
 
 
Next, you find b. 
Use the triangle relationship,  .  You already know the value for c, 
 , and you already just found a. 
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