Hello, I need some help solving and explaining the next problems: 1) Using Riemann sums check that: \int _a^b3x^2dx=b^3-a^3\:∫ a b ​ 3x 2 dx=b 3 −a 3  2)Using Riemann sums, calculate: \int _1^3\left(4x^3-3x^2+1\right)dx∫ 1 3 ​ (4x 3 −3x 2 +1)dx