Summation for volume of a sphere?

Question

Hey trying to get this equation worked out for a bigger equations but I cant get the answer myself and need help ...

(4/3*π*1^3)+(4/3*π*2^3)+(4/3*π*3^3) = 150.796^3

How do you get it to work like easier summations such as this without the cubed radius

(4/3*π*1)+(4/3*π*2)+(4/3*π*3) = 25.132
Sigma 1->3 = nπ -> n=((3+1)3)/2

Answer 1

(4/3*π*1³)+(4/3*π*2³)+(4/3*π*3³) = 150.796³

^{Take out the common factor}

= (4/3*π) * (1³+2³+3³)

We know that Sums of Powers of Integers :