SOLUTION: Find the center,foci,vertices and covertices of the ellipse with the given equation. 9x^2+16y^2-126x+64y=71

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Question 1043225: Find the center,foci,vertices and covertices of the ellipse with the given equation.
9x^2+16y^2-126x+64y=71

Answer by ikleyn(52790) About Me  (Show Source):
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Find the center,foci,vertices and covertices of the ellipse with the given equation.
9x^2+16y^2-126x+64y=71
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9x%5E2%2B16y%5E2-126x%2B64y = 71  --->

9%2A%28x%5E2-14x%29+%2B+16%2A%28y%5E2%2B4y%29 = 71  --->

9%2A%28x-7%29%5E2+-+9%2A49+%2B+16%2A%28y%2B2%29%5E2+-+16%2A4 = 171,

9%2A%28x-7%29%5E2+%2B+16%2A%28y%2B2%29%5E2 = 171%2B9%2A49+%2B+16%2A4,

9%2A%28x-7%29%5E2+%2B+16%2A%28y%2B2%29%5E2 = 171%2B9%2A49+%2B+16%2A4,

9%2A%28x-7%29%5E2+%2B+16%2A%28y%2B2%29%5E2 = 676,      ( <--- next divide both sides by 676 = 26%5E2 )

%28x-7%29%5E2%2F%2826%2F3%29%5E2+%2B+%28y%2B2%29%5E2%2F%2826%2F4%29%5E2 = 1,  or

%28x-7%29%5E2%2F%2826%2F3%29%5E2+%2B+%28y%2B2%29%5E2%2F%2813%2F2%29%5E2 = 1.

The center of the ellipse is the point  (7,-2).

The semi-major axis is a = 26%2F3.

The semi-minor axis is b = 26%2F4 = 13/2.   (Notice that a > b. The major axis is horizontal, and the ellipse is wider than tall).

Two vertices in horizontal directions are  (7%2B%2826%2F3%29,-2)  and  (7-%2826%2F3%29,-2).

Two vertices in vertical directions are  (7,-2%2B%2813%2F2%29)  and  (7,-2-%2813%2F2%29).

The linear eccentricity is c = sqrt%28a%5E2-b%5E2%29 = sqrt%28%2826%2F3%29%5E2-%2826%2F4%29%5E2%29 = 26%2Asqrt%28%281%2F9%29-%281%2F16%29%29 = 26%2Asqrt%28%2816-9%29%2F%289%2A16%29%29 = %2826%2F%283%2A4%29%29%2Asqrt%287%29 = %2813%2F6%29%2Asqrt%287%29.

The foci are  (7%2B%2813%2F6%29sqrt%287%29,-2)  and  (7-%2813%2F6%29sqrt%287%29,-2).

See the lesson
    - Ellipse definition, canonical equation, characteristic points and elements
in this site.