The graph of \(g\) is shown. Define \(I_0(x)=\int_0^x g(t)\,dt\).
a) Use geometric areas to find \(I_0(4)\) and \(I_0(8)\).
b) Find where \(I_0\) reaches its maximum on \([0,8]\), and give the maximum value.
c) Describe the graph of \(I_0\) on \([0,8]\), including key points and its shape between them.

Hints
- Interpret the accumulation function as signed area.
- Find the areas of the triangles above and below the x-axis.
- Use the sign of \(g\) to determine where \(I_0\) increases or decreases.
- The antiderivative of a linear function is quadratic.
Solution
1. a) From \(0\) to \(4\), the graph forms a triangle above the x-axis with base \(4\) and height \(2\). Thus, \(I_0(4)=\frac{1}{2}\cdot4\cdot2=4\).
2. From \(4\) to \(8\), the graph forms an equal triangle below the x-axis, contributing \(-4\). Therefore, \(I_0(8)=4-4=0\).
3. b) The derivative of \(I_0\) is \(g\). Since \(g>0\) on \((0,4)\) and \(g<0\) on \((4,8)\), \(I_0\) increases and then decreases. Its maximum occurs at \(x=4\), with value \(4\).
4. c) The graph begins at \((0,0)\), passes through \((2,2)\), reaches its maximum at \((4,4)\), passes through \((6,2)\), and ends at \((8,0)\). Because \(g\) is piecewise linear, \(I_0\) consists of connected parabolic arcs.
Answer
a) \(I_0(4)=4\) and \(I_0(8)=0\)
b) The maximum value is \(4\), attained at \(x=4\).
c) The graph passes through \((0,0)\), \((2,2)\), \((4,4)\), \((6,2)\), and \((8,0)\), using connected parabolic arcs.