The Attempt at a SolutionReduce Ellipse: Centre & Eccentricity

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    Ellipse Reduction
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SUMMARY

The discussion focuses on reducing the ellipse given by the equation 4(x-2y+1)² + 9(2x+y+2)² = 25 into standard form to find its center and eccentricity. By substituting X = x - 2y and Y = 2x + y, the equation simplifies to (4/25)(X + 1)² + (9/25)(Y + 2)² = 1. The center of the ellipse is located at (-1, -2) and the eccentricity can be derived from the coefficients of the standard form equation.

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Homework Statement


Reduce the given ellipse in standard form and find its centre and eccentricity.

4(x-2y+1)2 + 9(2x+y+2)2 = 25

Homework Equations



Rotation of axes
x=Xcosθ - Ysinθ
y=Xsinθ + Ycosθ
 
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I would not use the "rotation of axes" formulas. Instead, let X= x- 2y and Y= 2x+ y so that your equation becomes
\frac{4}{25}(X- (-1))^2+ \frac{9}{25}(Y- (-2))^2= 1

What is the center and eccentricity of that ellipse? Now go back to x and y coordinates.
 
Wow! that is a very nice method. Thanks!
 

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