I don't understand Left and Right riemann sums. If you could help Please estimate the value of the definite integral using a LEFT Riemann Sum with 3 EQUAL SUBINTERVALS. Integral with 4 on top and 1 underneath (x^2+3)dx

Select the correct answer. what was edwin hubble's contribution to the field of astronomy? a. he discovered variable stars. b. he proved that the heliocentric model accurately described our solar system. c. he found a relationship between the period luminosity and distance of stars. d. he proved that the universe is finite. e. he discovered that the universe was expanding.