Math Problem Statement

Find the integral of a piecewise linear function f(x) from 0 to various points (b = 2, 4, 7, 10).

Solution

To solve this problem, we interpret F(x)=f(x)F'(x) = f(x), and F(0)=0F(0) = 0, to find F(b)F(b) at the given points b=2,4,7,b = 2, 4, 7, and 1010. The function F(x)F(x) is the integral of f(x)f(x), so:

F(b)=0bf(x)dxF(b) = \int_0^b f(x) \, dx

The graph of f(x)f(x) is a piecewise linear function, and the area under the curve is calculated geometrically (e.g., using areas of triangles and rectangles). Let’s calculate F(b)F(b):

Step 1: Break the integral into parts

  1. For b=2b = 2, we compute the area under f(x)f(x) from x=0x = 0 to x=2x = 2.
  2. Similarly for b=4,7,10b = 4, 7, 10, calculate areas up to these points.

Step 2: Compute the areas geometrically

  1. From x=0x = 0 to x=2x = 2: The graph shows a triangle with base 2 and height 2. Area=12×2×2=2\text{Area} = \frac{1}{2} \times 2 \times 2 = 2 Therefore, F(2)=2F(2) = 2.

  2. From x=0x = 0 to x=4x = 4: Add the rectangle from x=2x = 2 to x=4x = 4 (base 2, height 2). Area of rectangle=2×2=4\text{Area of rectangle} = 2 \times 2 = 4 Total F(4)=2+4=6F(4) = 2 + 4 = 6.

  3. From x=0x = 0 to x=7x = 7: Include the triangle from x=4x = 4 to x=7x = 7 (base 3, height 3). Area of triangle=12×3×3=4.5\text{Area of triangle} = \frac{1}{2} \times 3 \times 3 = 4.5 Total F(7)=6+4.5=10.5F(7) = 6 + 4.5 = 10.5.

  4. From x=0x = 0 to x=10x = 10: Subtract the area below the x-axis (from x=7x = 7 to x=10x = 10, base 3, height -3). Negative area of triangle=12×3×3=4.5\text{Negative area of triangle} = -\frac{1}{2} \times 3 \times 3 = -4.5 Total F(10)=10.54.5=6F(10) = 10.5 - 4.5 = 6.

Final Table:

\hline b & F(b) \\ \hline 2 & 2 \\ 4 & 6 \\ 7 & 10.5 \\ 10 & 6 \\ \hline \end{array}$$ Let me know if you need more explanation or further breakdown! --- **5 Related Questions**: 1. How can you calculate the integral of a piecewise linear function geometrically? 2. What is the relationship between a derivative and the integral of a function? 3. Why does the integral's sign change when the graph goes below the x-axis? 4. How do we apply the Fundamental Theorem of Calculus in such problems? 5. Can we generalize the calculation for arbitrary $$b$$? **Tip**: When integrating piecewise linear graphs, always sketch sub-intervals to simplify area calculations.

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Math Problem Analysis

Mathematical Concepts

Calculus
Integration
Piecewise Functions
Geometric Interpretation of Integrals

Formulas

F(b) = ∫₀ᵇ f(x) dx
Area of a triangle = (1/2) × base × height
Area of a rectangle = base × height

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12