Wait sorry in fraction for it is 1000000/10
Let
. The tangent plane to the surface at (0, 0, 8) is

The gradient is

so the tangent plane's equation is

The normal vector to the plane at (0, 0, 8) is the same as the gradient of the surface at this point, (1, 1, 1). We can get all points along the line containing this vector by scaling the vector by
, then ensure it passes through (0, 0, 8) by translating the line so that it does. Then the line has parametric equation

or
,
, and
.
(See the attached plot; the given surface is orange, (0, 0, 8) is the black point, the tangent plane is blue, and the red line is the normal at this point)
Answer:
1. 4.66 gallons 2. 2.33 gallons 3. 1.55 gallons
Step-by-step explanation:
1. If her gallons cover is 250 square feet, the number of gallons of paint Lacie would need to cover 1,165.5 square feet of bedroom walls is
1,165.5/250 = 4.66 gallons
2. If her gallons cover is 500 square feet, the number of gallons of paint Lacie would need to cover 1,165.5 square feet of bedroom walls is
1,165.5/500 = 2.33 gallons
3. If her gallons cover is 750 square feet, the number of gallons of paint Lacie would need to cover 1,165.5 square feet of bedroom walls is
1,165.5/750 = 1.55 gallons
OK, so the graph is a parabola, with points x=0,y=0; x=6,y=-9; and x=12,y=0
Because the roots of the equation are 0 and 12, we know the formula is therefore of the form
y = ax(x - 12), for some a
So put in x = 6
-9 = 6a(-6)
9 = 36a
a = 1/4
So the parabola has a curve y = x(x-12) / 4, which can also be written y = 0.25x² - 3x
The gradient of this is dy/dx = 0.5x - 3
The key property of a parabolic dish is that it focuses radio waves travelling parallel to the y axis to a single point. So we should arrive at the same focal point no matter what point we chose to look at. So we can pick any point we like - e.g. the point x = 4, y = -8
Gradient of the parabolic mirror at x = 4 is -1
So the gradient of the normal to the mirror at x = 4 is therefore 1.
Radio waves initially travelling vertically downwards are reflected about the normal - which has a gradient of 1, so they're reflected so that they are travelling horizontally. So they arrive parallel to the y axis, and leave parallel to the x axis.
So the focal point is at y = -8, i.e. 1 metre above the back of the dish.
Answer:
yo emanuael
Step-by-step explanation: