Consider the given points above on and plane.
An ellipse pass through above points whose equation can be written as
Where are all integers and
Find the value of .
Inspired from this problem.
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We can write a x 2 + b y 2 + c x y + d x + e y + f = 0 as follows:
a x 2 + b y 2 + c x y + d x + e y + f x 2 + a b y 2 + a c x y + a d x + a e y + a f a b y 2 + a c x y + a d x + a e y + a f = 0 = 0 = − x 2
Substituting the values of ( x , y ) of the five points, we have the following matrix equation.
⎣ ⎢ ⎢ ⎢ ⎢ ⎡ 1 6 9 0 4 0 9 6 6 4 1 − 1 3 0 0 − 8 3 2 7 2 0 − 1 0 3 − 1 3 9 0 1 3 0 6 4 8 − 1 1 1 1 1 1 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ a b a c a d a e a f ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ − 1 0 0 − 9 − 1 6 9 − 8 1 0 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤
⎣ ⎢ ⎢ ⎢ ⎢ ⎡ a b a c a d a e a f ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ 1 6 9 0 4 0 9 6 6 4 1 − 1 3 0 0 − 8 3 2 7 2 0 − 1 0 3 − 1 3 9 0 1 3 0 6 4 8 − 1 1 1 1 1 1 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ − 1 ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ − 1 0 0 − 9 − 1 6 9 − 8 1 0 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ − 0 . 0 0 1 4 2 5 − 0 . 0 0 2 8 4 9 − 0 . 0 1 7 0 9 4 0 . 0 4 9 8 5 8 0 . 0 5 1 2 8 2 − 0 . 0 0 5 8 0 9 − 0 . 0 3 5 0 5 6 0 . 3 3 6 5 3 8 − 0 . 0 1 5 4 2 5 − 0 . 0 0 9 6 1 5 0 . 0 0 0 2 8 9 − 0 . 0 0 0 0 2 2 0 . 0 0 1 0 6 8 − 0 . 0 0 2 9 1 6 − 0 . 0 0 3 2 0 5 0 . 0 0 0 7 7 2 0 . 0 0 8 4 8 8 − 0 . 0 1 8 5 1 9 0 . 0 5 6 3 2 7 0 . 0 5 5 5 5 6 0 . 0 0 6 1 7 3 0 . 0 2 9 4 4 0 − 0 . 3 0 1 9 9 4 − 0 . 0 8 7 8 4 4 0 . 9 0 5 9 8 3 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ − 1 0 0 − 9 − 1 6 9 − 8 1 0 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ 0 . 0 8 3 3 3 3 3 3 3 − 0 . 0 8 3 3 3 3 3 3 3 0 − 8 . 9 1 6 6 6 6 6 6 7 − 9 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎢ ⎡ 1 2 1 − 1 2 1 0 1 2 1 0 7 − 9 ⎦ ⎥ ⎥ ⎥ ⎥ ⎤
⇒ a = 1 2 , b = 1 , c = − 1 , d = 0 , e = − 1 0 7 , f = − 1 0 8 ⇒ ∣ a ∣ + ∣ b ∣ + ∣ c ∣ + ∣ d ∣ + ∣ e ∣ + ∣ f ∣ = 1 2 + 1 + 1 + 0 + 1 0 7 + 1 0 8 = 2 2 9
Note: I have solved the inverse matrix using Excel.