Mark M. answered 02/05/24
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
Between x = 0 and x = 6, the graph of f(x) is the horizontal line segment with endpoints (0,6) and (6,6).
Between x = 6 and x = 10, the graph of f(x) is the line segment with endpoints (6,6) and (10,10).
∫(0 to 10) f(x)dx = area below the graph of f(x) and above the x-axis between x = 0 and x = 10.
= (area between x = 0 and x = 6) + (area between x = 6 and x = 10)
= (area of rectangle with length = width = 6) + (area of trapezoid with bases 6 and 10 and height 4)
= (6)(6) + (1/2)(6 + 10)(4) = 36 + 32 = 68