Posted on 2009-04-06
Consider the line perpendicular to the surface z = x2 + y2 at the point (3, 4, 25).
Which of the following vectors is normal to the surface at the given point?
Below is the answer key that I don't understand
Equation of the surface
at the point (3,4,25) the eqn of the tgt plane is
x(3)+y(4)-(1/2)(z+25)=0 ==> 6x+8y-z=25
where did they get the formula x(3)+y(4)-(1/2)(z+25)=0 from?