Check the picture below.
if you go from the slant height, the path is shorter to the top, since the hypotenuse is the longest of all sides in a right-triangle.
that said, is shorter but is also steeper, so the lateral edge is longer but less steep and thus a bit simpler though longer, but we're only asked on which is shorter.
1,000,000 is written as 10^6. Other wise it would be too low or too high.
D) 36x^2-81
both 36x^2 and -81 are perfect squares
difference means subtraction