Math Problem Statement

Use areas to evaluate ∫2−1(1−2x)dx∫−12(1−2x)dx.

A.

33

B.

55

C.

22

D.

1010

E.

00

Solution

We are tasked with evaluating the expression

21(12x)dx12(12x)dx\int_{2}^{-1} (1 - 2x) \, dx \int_{-1}^{2} (1 - 2x) \, dx

This consists of two integrals that need to be evaluated individually, and then we find the product of their results. Let’s compute each integral step-by-step.

Step 1: Evaluate 21(12x)dx\int_{2}^{-1} (1 - 2x) \, dx

We will first compute the integral (12x)dx\int (1 - 2x) \, dx:

(12x)dx=xx2+C\int (1 - 2x) \, dx = x - x^2 + C

Now, we apply the limits from 2 to -1:

[ \left[ x - x^2 \right]_{2}^{-1} = \left[ (-1) - (-1)^2 \right] - \left[ 2 - 2^2 \right] ] =(11)(24)=(2)(2)=2+2=0= (-1 - 1) - (2 - 4) = (-2) - (-2) = -2 + 2 = 0

So, the first integral evaluates to 00.

Step 2: Evaluate 12(12x)dx\int_{-1}^{2} (1 - 2x) \, dx

We now compute the same integral, but with limits from -1 to 2:

[ \left[ x - x^2 \right]_{-1}^{2} = \left[ 2 - 2^2 \right] - \left[ (-1) - (-1)^2 \right] ] =(24)(11)=(2)(2)=2+2=0= (2 - 4) - (-1 - 1) = (-2) - (-2) = -2 + 2 = 0

So, the second integral also evaluates to 00.

Step 3: Product of the two integrals

Since both integrals result in 00, their product is:

0×0=00 \times 0 = 0

Thus, the value of the entire expression is 0\boxed{0}, which corresponds to option E.


Would you like further details on the method used?

Here are some additional questions to consider:

  1. What is the geometric interpretation of the integral in this problem?
  2. How would the result change if the function were different?
  3. Can you describe how symmetry plays a role in integrals like these?
  4. What happens if we reverse the limits of integration?
  5. How do integrals of polynomial functions behave when evaluated over symmetric intervals?

Tip: When the result of an integral over symmetric limits is zero, it often suggests that the area above and below the x-axis cancels out.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Integral Calculus
Definite Integrals
Areas Under Curves

Formulas

∫ (1 - 2x) dx = x - x^2

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12