y = −6x2 + 8, y = 2,
12.5.z = x − x2 − y2 −1, z = x − x2 − y2 − 5.
x = 5y2 − 9, x = −4,
12.7.z = x2 + 4x − y2 − 4, z = x2 + 4x − y2 + 2.
x = 5y2 −1, x = −3y2 +1,
12.9.z = 2 − x2 + 6y2 , z = −1− x2 + 6y2 .
y = −5x2 + 3, y = −2,
12.11.z = 2x2 − 3y − 6y2 −1, z = 2x2 − 3y − 6y2 + 2.
x = 3y2 − 5, x = −2,
12.13.z = 2 − x2 +16y2 , z = 8 − x2 +16y2 .
y = 2x2 −1, y =1,
12.15.z = x2 − 5y2 − 3, z = x2 − 5y2 − 6.
x = −4y2 +1, x = −3,
12.17.z = x2 − 7y2 −1, z = x2 − 7y2 + 2.
y =1− 2x2 , y = −1,
12.19.z = x2 + 2y + y2 − 2, z = x2 + 2y + y2 +1.
y= 5x2 −1, y = −3x2 +1,
12.6.z = −2 + 3x2 + y2 , z = −5 + 3x2 + y2 .
y= 6x2 −1, y = 5,
12.8.z = 2x2 + x − y2 ,
z = 2x2 + x − y2 + 4.
x = −3y2 + 7, x = 4,
12.10.z = 2 + 6x2 + y2 , z = 3+ 6x2 + y2 .
y = x2 − 5, y = −x2 + 3,
12.12.z = 4 + 5x2 + 8y2 , z =1+ 5x2 + 8y2 .
x = y2 − 2, x = −4y2 + 3,
12.14.z = 16 − x2 − y2 + 2, z = 16 − x2 − y2 −1.
y = x2 − 2, y = −4x2 + 3,
12.16.z = 2 + x2 + y2 , z = −1+ x2 + y2 .
x = 7y2 − 6, x = −2y2 + 3,
12.18.z = 3−12y2 + 5x2 , z = −2 −12y2 + 5x2.
y = x2 − 7, y = −8x2 + 2,
12.20.z = 3−12y2 + 5x2 , z = −2 −12y2 + 5x2.