4. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
5. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x :
x a
6. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
7. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
y
y x 1
1
1 x
8. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
y
y x 1
1
1 x
lim x 1 0
x1
9. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
y y
y x 1 6
4 y f x
1
1 x x
lim x 1 0
x1
10. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
y y
y x 1 6
4 y f x
1
1 x x
lim x 1 0
lim f x 4
x1 x0
11. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
lim f x :
x a
y y
y x 1 6
4 y f x
1
1 x x
lim x 1 0
lim f x 4
x1 x0
12. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
lim f x : as the x value approaches a from the positive side,
x a
what value does f(x) approach?
y y
y x 1 6
4 y f x
1
1 x x
lim x 1 0
lim f x 4
x1 x0
13. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
lim f x : as the x value approaches a from the positive side,
x a
what value does f(x) approach?
y y
y x 1 6
4 y f x
1
1 x x
lim x 1 0
lim x 1 0
lim f x 4
x1 x1 x0
14. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
lim f x : as the x value approaches a from the positive side,
x a
what value does f(x) approach?
y y
y x 1 6
4 y f x
1
1 x x
lim x 1 0
lim x 1 0
lim f x 4
lim f x 6
x1 x1 x0 x0
15. Limits & Continuity
A limit describes the behaviour of functions.
lim f x : as the x value approaches a, what value does f(x) approach?
x a
lim f x : as the x value approaches a from the negative side,
x a
what value does f(x) approach?
lim f x : as the x value approaches a from the positive side,
x a
what value does f(x) approach?
y y
y x 1 6
4 y f x
1
1 x x
lim x 1 0
lim x 1 0
lim f x 4
lim f x 6
x1 x1 x0 x0
If lim f x lim f x , then f x is continuous at x a
x a x a
21. Finding Limits
(1) Direct Substitution
e.g. lim x 7 5 7
x5
12
(2) Factorise and Cancel
x2 9
e.g. lim
x3 x 3
22. Finding Limits
(1) Direct Substitution
e.g. lim x 7 5 7
x5
12
(2) Factorise and Cancel
e.g. lim
x2 9
lim
x 3 x 3
x3 x 3 x3 x 3
23. Finding Limits
(1) Direct Substitution
e.g. lim x 7 5 7
x5
12
(2) Factorise and Cancel
e.g. lim
x2 9
lim
x 3 x 3
x3 x 3 x3 x 3
lim x 3
x3
24. Finding Limits
(1) Direct Substitution
e.g. lim x 7 5 7
x5
12
(2) Factorise and Cancel
e.g. lim
x2 9
lim
x 3 x 3
x3 x 3 x3 x 3
lim x 3
x3
33
6
27. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
e.g. i lim
x 4 x3 1
28. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
x3 3x 2 2 x 1 3 3 3
e.g. i
3
lim lim x x x x
x 4x 1
3
x 4 x3 1
3
3
x x
29. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
x3 3x 2 2 x 1 3 3 3
e.g. i
3
lim lim x x x x
x 4x 1
3
x 4 x3 1
3
3
x x
3 2 1
1 2 3
lim x x x
x 1
4 3
x
30. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
x3 3x 2 2 x 1 3 3 3
e.g. i
3
lim lim x x x x
x 4x 1
3
x 4 x3 1
3
3
x x
3 2 1
1 2 3
lim x x x
x 1
4 3
x
1
4
31. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
x3 3x 2 2 x 1 3 3 3
e.g. i
3
lim lim x x x x
x 4x 1
3
x 4 x3 1
3
3
x x
3 2 1
1 2 3
lim x x x
x 1
4 3
x
1
4
4x x2
ii lim 3
x x 1
32. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
x3 3x 2 2 x 1 3 3 3
e.g. i
3
lim lim x x x x
x 4x 1
3
x 4 x3 1
3
3
x x
3 2 1
1 2 3
lim x x x
x 1
4 3
x
1
4
4x x2 0
ii lim 3
x x 1
1
0
33. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
x3 3x 2 2 x 1 3 3 3
e.g. i
3
lim lim x x x x
x 4x 1
3
x 4 x3 1
3
3
x x
3 2 1
1 2 3
lim x x x
x 1
4 3
x
1
4
4x x2 0 x7 x6 x2
ii lim 3
x x 1
iii lim 7
x 3 x x 974
1
0
34. (3) Special Limit
1
lim 0
x x
x3 3x 2 2 x 1
x3 3x 2 2 x 1 3 3 3
e.g. i
3
lim lim x x x x
x 4x 1
3
x 4 x3 1
3
3
x x
3 2 1
1 2 3
lim x x x
x 1
4 3
x
1
4
4x x2 0 x7 x6 x2 1
ii lim 3
x x 1
iii lim 7
x 3 x x 974
1 3
0
37. x3 2 1
iv lim 2
x x 1
0
x 3 x 2
v Find the horizontal asymptote of y
x 1 x 1
38. x3 2 1
iv lim 2
x x 1
0
x 3 x 2
v Find the horizontal asymptote of y
x 1 x 1
lim
x 3 x 2
x x 1 x 1
39. x3 2 1
iv lim 2
x x 1
0
x 3 x 2
v Find the horizontal asymptote of y
x 1 x 1
x 3 x 2 x2 x 6
lim lim 2
x x 1 x 1 x x 1
40. x3 2 1
iv lim 2
x x 1
0
x 3 x 2
v Find the horizontal asymptote of y
x 1 x 1
x 3 x 2 x2 x 6
lim lim 2
x x 1 x 1 x x 1
1
1
1
41. x3 2 1
iv lim 2
x x 1
0
x 3 x 2
v Find the horizontal asymptote of y
x 1 x 1
x 3 x 2 x2 x 6
lim lim 2
x x 1 x 1 x x 1
1
1
1
horizontal asymptote is y 1
42. x3 2 1
iv lim 2
x x 1
0
x 3 x 2
v Find the horizontal asymptote of y
x 1 x 1
x 3 x 2 x2 x 6
lim lim 2
x x 1 x 1 x x 1
1
1
1
horizontal asymptote is y 1 Exercise 7I; 1a, 2ace, 3ac,
4a, 5ad, 8a, 9ab, 10a