CPM Homework Help : CALC Problem 12-41

Multiple Choice: The function $f$ is continuous on the closed interval $[3, 9]$ and has values given in the table below.

$x$	$3$	$4$	$7$	$9$
$f(x)$	$50$	$40$	$20$	$30$

Using the subintervals $[3, 4]$ , $[4, 7]$ , and $[7, 9]$ , what is the trapezoidal approximation of $\int _ { 3 } ^ { 9 } f ( x ) d x$ ?

Hint:

Be careful! The subintervals have different widths.