quadrica

a = -1.9 (slider from -5 to 5)
b = -3.4 (slider from -5 to 5)
c = 2.6 (slider from -5 to 5)
d: x^(2) / a^(2) + y^(2) / b^(2) - z^(2) / c^(2) = 1
e: x^(2) / a^(2) - y^(2) / b^(2) + z^(2) / c^(2) = 1