Bài tập và đáp án
Bài tập 1: Giải các phương trình bậc hai sau:

TT
PTBH
TT
PTBH

1
x2 - 11x + 30 = 0
41
x2 - 16x + 84 = 0

2
x2 - 10x + 21 = 0
42
x2 + 2x - 8 = 0

3
x2 - 12x + 27 = 0
43
5x2 + 8x + 4 = 0

4
5x2 - 17x + 12 = 0
44
x2 – 2x + 4= 0

5
3x2 - 19x - 22 = 0
45
11x2 + 13x - 24 = 0

6
x2 - (1x + = 0
46
x2 - 11x + 30 = 0

7
x2 - 14x + 33 = 0
47
x2 - 13x + 42 = 0

8
6x2 - 13x - 48 = 0
48
11x2 - 13x - 24 = 0

9
3x2 + 5x + 61 = 0
49
x2 - 13x + 40 = 0

10
x2 - x - 2 = 0
50
3x2 + 5x - 1 = 0

11
x2 - 24x + 70 = 0
51
5x2 + 7x - 1 = 0

12
x2 - 6x - 16 = 0
52
3x2 - 2x - 3 = 0

13
2x2 + 3x + 1 = 0
53
x2 - 2x + 1 = 0

14
x2 - 5x + 6 = 0
54
x2 - 2x - 2= 0

15
3x2 + 2x + 5 = 0
55
11x2 + 13x + 24 = 0

16
2x2 + 5x - 3 = 0
56
x2 + 13x + 42 = 0

17
x2 - 7x - 2 = 0
57
11x2 - 13x - 24 = 0

18
3x2 - 2x - 2 = 0
58
2x2 - 3x - 5 = 0

19
-x2 - 7x - 13 = 0
59
x2 - 4x + 4 = 0

20
x2 – 2x -3= 0
60
x2 - 7x + 10 = 0

21
3x2 - 2x - 1 = 0
61
4x2 + 11x - 3 = 0

22
x2 - 8x + 15 = 0
62
3x2 + 8x - 3 = 0

23
2x2 + 6x + 5 = 0
63
x2 + x + 1 = 0

24
5x2 + 2x - 3 = 0
64
x2 + 16x + 39 = 0

25
x2 + 13x + 42 = 0
65
3x2 - 8x + 4 = 0

26
x2 - 10x + 2 = 0
66
4x2 + 21x - 18 = 0

27
x2 - 7x + 10 = 0
67
4x2 + 20x + 25 = 0

28
5x2 + 2x - 7 = 0
68
2x2 - 7x + 7 = 0

29
4x2 - 5x + 7 = 0
69
-5x2 + 3x - 1 = 0

30
x2 - 4x + 21 = 0
70
x2 - 2x - 6 = 0

31
5x2 + 2x -3 = 0
71
x2 - 9x + 18 = 0

32
4x2 + 28x + 49 = 0
72
3x2 + 5x + 4 = 0

33
x2 - 6x + 48 = 0
73
x2 + 5 = 0

34
3x2 - 4x + 2 = 0
74
x2 - 4 = 0

35
x2 - 16x + 84 = 0
75
x2 - 2x = 0

36
x2 + 2x - 8 = 0
76
x4 - 13x2 + 36 = 0

37
5x2 + 8x + 4 = 0
77
9x4 + 6x2 + 1 = 0

38
x2 – 2x + 4= 0
78
2x4 + 5x2 + 2 = 0

39
x2 - 6x + 8 = 0
79
2x4 - 7x2 - 4 = 0

40
3x2 - 4x + 2 = 0
80
x4 - 5x2 + 4 = 0

Bài tập 2. Tìm x, y trong các trường hợp sau:
a)
x + y = 17, x.y = 180
e)
x2 + y2 = 61 , x.y = 30

b)
x + y = 25, x.y = 160
f)
x - y = 6, x.y = 40

c)
x + y = 30, x2 + y2 = 650