Answer:
4x+y add like terms ... -5+9=4 and -y(or -1)+2y=y
I assume there are some plus signs that aren't rendering for some reason, so that the plane should be

.
You're minimizing

subject to the constraint

. Note that

and

attain their extrema at the same values of

, so we'll be working with the squared distance to avoid working out some slightly more complicated partial derivatives later.
The Lagrangian is

Take your partial derivatives and set them equal to 0:

Adding the first three equations together yields

and plugging this into the first three equations, you find a critical point at

.
The squared distance is then

, which means the shortest distance must be

.
Answer:
Pythagorean Theorem: c2 = a2 + b2
Find the area by adding the areas of the three triangles. The area of a right triangle is: A = ½bh
Two triangles are identical so you can just multiply the area of the first triangle by two: 2A1 = 2(½bh) = 2(½ab) = ab.
The total area of the trapezoid is : A1 + A2 = ab + ½c2
You multiply both sides by 2 to get rid of the ½: (a2 + 2ab + b2) = 2ab + c2
You subtract out the 2ab: a2 + b2 = c2.
Then what is left is the proof: a2 + b2 = c2
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The amount of balls in a given layer can be found by squaring the layer it is in
4 layers
top layer (1st) is 1
2nd is 4
3rd layer is 9
4th is 16
add them up
1+4+9+16=30
30 in that pyramid