Question

Write the equation of the sphere in standard form.
x2 + y2 + z2 + 4x − 2y − 2z = 19

Answer 1

come on - you did this for 2D figures back in Algebra II:

x^2+4x + y^2-2y + z^2-2z = 19
x^2+4x+4 + y^2-2y+1 = z^2-2z+1 = 19+4+1+1
(x+2)^2 + (y-1)^2 + (z-1)^2 = 25

Answer 2

Just needed a refresher. Thanks.