The teacher will be very surprised to see your correct solution 😉
2 2 -100 - 12*x + 3*x + 8*y + 32*y = 0
3*x^2 - 12*x + 8*y^2 + 32*y - 100 = 0
2 2
\tilde x \tilde y
---------- + ---------- = 1
2 2
// ___\\ // ___\\
||\/ 3 || ||\/ 2 ||
||-----|| ||-----||
|\ 3 /| |\ 4 /|
|-------| |-------|
\ 1/12 / \ 1/12 / (2, -2)
|a11 a12|
I2 = | |
|a12 a22| |a11 a13| |a22 a23|
K2 = | | + | |
|a13 a33| |a23 a33| |3 0|
I2 = | |
|0 8| |3 -6 | |8 16 |
K2 = | | + | |
|-6 -100| |16 -100| 2 2
\tilde x \tilde y
---------- + ---------- = 1
2 2
// ___\\ // ___\\
||\/ 2 || ||\/ 3 ||
||-----|| ||-----||
|\ 4 /| |\ 3 /|
|-------| |-------|
\ 1/12 / \ 1/12 /