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Definite integralsCalculusCollegeabout 0:48

Integrate abs(x) from -2 to -1: animated lesson

A narrated, step-by-step definite integrals video lesson with captions. Final answer: 3/2 ≈ 1.5.

Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.3 MB) · Captions (WebVTT)

Steps on screen

  1. 1. The problem
    Evaluating an integral
    ∫−2−1∣x∣ dx\int_{-2}^{-1} \left| x\right|\,dx
  2. 2. Step by step
    1. ∫−2−1∣x∣ dx\int_{-2}^{-1} \left| x\right|\,dx
      Start with the definite integral
    2. ∫∣x∣ dx=x⋅∣x∣2\int \left| x\right|\,dx = \frac{x\cdot\left| x\right|}{2}
      ∫ |u| du = u|u|/2
    3. F(x)=x⋅∣x∣2F(x) = \frac{x\cdot\left| x\right|}{2}
      Antiderivative
    4. F(−1)−F(−2)=−0.5−(−2)=32≈1.5F(-1) - F(-2) = -0.5 - \left(-2\right) = \frac{3}{2} \approx 1.5
      Apply the fundamental theorem of calculus
  3. 3. The answer
    ∫−2−1∣x∣ dx=32≈1.5\int_{-2}^{-1} \left| x\right|\,dx = \frac{3}{2} \approx 1.5

    ∫ from -2 to -1 = 3/2 ≈ 1.5

  4. 4. Check
    • Differentiated the antiderivative and compared it with the integrand ✓
    • Adaptive Simpson's rule gives 1.5 ✓

Transcript

The problem. Here is the problem: integrate abs(x) from negative 2 to negative 1. Evaluate the definite integral of abs(x) from x equals negative 2 to x equals negative 1.

Step by step. Start with the definite integral. the integral of |u| du equals u|u|/2. Antiderivative. Apply the fundamental theorem of calculus.

The answer. So the answer is 3 over 2 approximately 1.5. A definite integral gives the signed area between the curve and the x-axis: area above the axis counts as positive and area below counts as negative.

Check. Differentiated the antiderivative and compared it with the integrand, which checks out. Adaptive Simpson prime s rule gives 1.5, which checks out.

About definite integrals

Evaluate definite integrals with the fundamental theorem of calculus.

Integrate abs(x) from -2 to -1: Animated Step-by-Step Lesson