What is the expression using summation notation of 0.4(1/2+1/2.4+1/2.8+1/3.2+1/3.6)?

30 determine the coefficient on x 12 y 24 x12y24 in ( x 3 + 2 x y 2 + y + 3 ) 18 . (x3+2xy2+y+3)18. (be careful, as x x and y y now appear in multiple terms! )

Two cities a and b are 1400km apart and lie on the same n-s line. the latitude of city a is 23 degrees. what is the latitude of city b. the radius of the earth is approximately 6400km.

The diameter of the moon is about 3500 km. approximate the surface area of the moon using the formula for the surface area of a sphere, s = 4πr2. write your answer in scientific notation.