a = 0.4 (slider from -5 to 5, step 0.1)
k = 1.6 (slider from -5 to 5, step 0.1)
a_k: ((x + y)^(2) * (y - a)^(2)) = (k^(2) * y^(2))
hund: ((x^(2) + y^(2)) * (y - a)^(2)) = (k^(2) * y^(2))
b_k: ((x^(2) + y^(2)) * (y^(2) - a^(2))) = (k^(2) * y^(2))
c_k: (x^(2) * (y - a)^(2)) = (y^(2) * (k^(2) - (y - a)^(2)))
d_k: (((k + y - a) * (k - y + a)) * y^(2)) = ((x * (y - a)))^(2)
e_k: (x^(2) * y^(2)) = ((y + a)^(2) * (k^(2) - y^(2)))
f: y = a