SumVenstre

SumVenstre[f,v,h,n]

f(x) = -0.14326592032067412 * x^(3.0) - 0.16257375075792435 * x^(2.0) + 0.5046622779014408 * x + 4.593141492327624
delta_x: (b - a) / n
List_x = Sequence(a + delta_x * (i - 1.0), i, 1.0, n + 1.0)
List_y: f(List_x)
List_r = Sequence(Polygon[(Element[List_x, i], 0.0), (Element[List_x, i + 1.0], 0.0), (Element[List_x, i + 1.0], Element[List_y, i]), (Element[List_x, i], Element[List_y, i])], i, 1.0, n)
Sum = Sum(List_r)