Dabour Hub EGEgyptian Curriculum 2026/2027
3-3 (b) Properties of the definite integral

3-3 (b) Properties of the definite integral

Point 8 of 12 — Lesson 1: Integration Techniques (Substitution and By Parts) and Definite IntegralsQuestion bank: 9 questions (9 with pictures)

08 3-3 (b) Properties of the definite integral

Rules

  • For a continuous f on [a,b] and c∈ ]a,b[:
  • ∫abf(x) dx=−∫baf(x) dx.
  • ∫aaf(x) dx=0.
  • ∫abf(x) dx=∫acf(x) dx+∫cbf(x) dx.
  • ∫abk f(x) dx=k∫abf(x) dx.
  • ∫ab[f(x)±g(x)] dx=∫abf(x) dx±∫abg(x) dx.
✍️ Worked examples

Example 15: If f is continuous on R, ∫13f(x) dx=6 and ∫53f(x) dx=−14, find ∫15f(x) dx.

Solution:

  • ∫15f(x) dx=∫13f(x) dx+∫35f(x) dx.
  • ∫35f(x) dx=−∫53f(x) dx=14.
  • ∫15f(x) dx=6+14=20.

The modulus function

  • Write ∣x−3∣=3−x for x<3 and x−3 for x≥3, then split the integral at x=3.
✍️ Worked examples

Example 16: Find ∫15∣x−3∣ dx.

Solution:

  • ∫15∣x−3∣ dx=∫13(3−x) dx+∫35(x−3) dx.
  • ∫13(3−x) dx=[3x−x22]13=(9−4.5)−(3−0.5)=2.
  • ∫35(x−3) dx=[x22−3x]35=(12.5−15)−(4.5−9)=2.
  • The total is 2+2=4 (two triangles, each of base 2 and height 2).

📝 Question bank for this point

9 questions linked to this point only, 9 of them with pictures.