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

Horizontal asymptote at  tells us that the original graph has been translated down.since  ,  are positive.  also we can say that the point  has a smaller  -coordinate than  .this means that the  transformed exponential function is increasing as it goes to the right. as it goes from  to , the value of the exponential function increases. it goes from to something bigger, . therefore, as  . the left hand would be the side that approaches the horizontal asymptote.so the answer is d