Math Problem Statement

solve

If \( \int_{-2}^{5} f(x) \, dx = 16 \), \( \int_{-2}^{5} g(x) \, dx = 4 \), and \( \int_{2}^{5} f(x) \, dx = 16 \), find the values of \( \int_{-2}^{2} f(x) \, dx \) and \( \int_{-2}^{5} [g(x) + 3] \, dx \).

Solution

Let's solve each part of the problem given the information provided.

Given Information:

  1. 25f(x)dx=16\int_{-2}^{5} f(x) \, dx = 16
  2. 25g(x)dx=4\int_{-2}^{5} g(x) \, dx = 4

We need to find the values of the following two integrals.


Problem 1

22f(x)dx\int_{-2}^{2} f(x) \, dx

To find 22f(x)dx\int_{-2}^{2} f(x) \, dx, we can use the fact that the integral over [2,5][-2, 5] is already given, and we can split this into two parts:

25f(x)dx=22f(x)dx+25f(x)dx\int_{-2}^{5} f(x) \, dx = \int_{-2}^{2} f(x) \, dx + \int_{2}^{5} f(x) \, dx

We know:

  • 25f(x)dx=16\int_{-2}^{5} f(x) \, dx = 16
  • 25f(x)dx=16\int_{2}^{5} f(x) \, dx = 16 (given directly in the problem)

Thus, 22f(x)dx=25f(x)dx25f(x)dx=1616=0\int_{-2}^{2} f(x) \, dx = \int_{-2}^{5} f(x) \, dx - \int_{2}^{5} f(x) \, dx = 16 - 16 = 0

So, 22f(x)dx=0\int_{-2}^{2} f(x) \, dx = 0


Problem 2

25[g(x)+3]dx\int_{-2}^{5} [g(x) + 3] \, dx

To evaluate this integral, we can separate it as follows:

25[g(x)+3]dx=25g(x)dx+253dx\int_{-2}^{5} [g(x) + 3] \, dx = \int_{-2}^{5} g(x) \, dx + \int_{-2}^{5} 3 \, dx

Now, compute each part:

  1. 25g(x)dx=4\int_{-2}^{5} g(x) \, dx = 4 (given directly).
  2. For 253dx\int_{-2}^{5} 3 \, dx:
    • This is the integral of a constant, which becomes 3×3 \times the length of the interval [2,5][-2, 5].
    • The length of the interval [2,5][-2, 5] is 5(2)=75 - (-2) = 7.
    • So, 253dx=3×7=21\int_{-2}^{5} 3 \, dx = 3 \times 7 = 21.

Adding these, we get: 25[g(x)+3]dx=4+21=25\int_{-2}^{5} [g(x) + 3] \, dx = 4 + 21 = 25


Final Answers

  1. 22f(x)dx=0\int_{-2}^{2} f(x) \, dx = 0
  2. 25[g(x)+3]dx=25\int_{-2}^{5} [g(x) + 3] \, dx = 25

Would you like a more detailed explanation of any steps or concepts used here?


Related Questions:

  1. What does it mean when we split an integral over two intervals?
  2. How do we calculate the integral of a constant over an interval?
  3. Why can we separate terms within an integral as shown in Problem 2?
  4. What is the importance of understanding the limits of integration?
  5. How would the answer change if 25f(x)dx\int_{-2}^{5} f(x) \, dx were different?

Tip:

When evaluating integrals with known values over specific intervals, look for opportunities to split or combine intervals strategically to simplify calculations.

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Math Problem Analysis

Mathematical Concepts

Definite Integration
Properties of Integrals

Formulas

\( \int_a^b f(x) \, dx = \int_a^c f(x) \, dx + \int_c^b f(x) \, dx \) (splitting integrals)
\( \int_a^b (f(x) + g(x)) \, dx = \int_a^b f(x) \, dx + \int_a^b g(x) \, dx \)

Theorems

Fundamental Theorem of Calculus
Linearity of Integration

Suitable Grade Level

Grades 11-12