3. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
4. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
5. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
6. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
7. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
8. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
e.g. (i ) Describe the roots of;
9. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
e.g. (i ) Describe the roots of;
a) 3x 2 5 x 9 0
10. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
e.g. (i ) Describe the roots of;
a) 3x 2 5 x 9 0
52 4 3 9
83 0
11. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
e.g. (i ) Describe the roots of;
a) 3x 2 5 x 9 0
52 4 3 9
83 0
no real roots
12. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
e.g. (i ) Describe the roots of;
a) 3x 2 5 x 9 0 b ) 2x 2 6 x 3 0
52 4 3 9
83 0
no real roots
13. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
e.g. (i ) Describe the roots of;
a) 3x 2 5 x 9 0 b ) 2x 2 6 x 3 0
52 4 3 9 62 4 2 3
83 0 60 0
no real roots
14. The Discriminant
b 2 4ac
The discriminant tells us whether the roots are rational or irrational
0 : two different real roots (cuts the x axis twice)
0 : two equal real roots (touches the x axis once)
0 : no real roots (never touches the x axis)
is a perfect square : roots are rational
e.g. (i ) Describe the roots of;
a) 3x 2 5 x 9 0 b ) 2x 2 6 x 3 0
52 4 3 9 62 4 2 3
83 0 60 0
no real roots two different, real, irrational roots
15. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
16. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
equal roots occur when 0
17. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
equal roots occur when 0
i.e. 62 4k 0
18. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
equal roots occur when 0
i.e. 62 4k 0
36 4k 0
k 9
19. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
equal roots occur when 0
i.e. 62 4k 0
36 4k 0
k 9
b) x 2 4 x 2k 0 have unreal roots
20. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
equal roots occur when 0
i.e. 62 4k 0
36 4k 0
k 9
b) x 2 4 x 2k 0 have unreal roots
unreal roots occur when 0
21. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
equal roots occur when 0
i.e. 62 4k 0
36 4k 0
k 9
b) x 2 4 x 2k 0 have unreal roots
unreal roots occur when 0
i.e. 4 4 2k 0
2
22. (ii) Find the values of k which makes;
a ) x 2 6 x k 0 have equal roots
equal roots occur when 0
i.e. 62 4k 0
36 4k 0
k 9
b) x 2 4 x 2k 0 have unreal roots
unreal roots occur when 0
i.e. 4 4 2k 0
2
16 8k 0
k 2
24. c) kx 2 2 x 4k 0 have real roots
real roots occur when 0
25. c) kx 2 2 x 4k 0 have real roots
real roots occur when 0
i.e. 22 4 k 4k 0
26. c) kx 2 2 x 4k 0 have real roots
real roots occur when 0
i.e. 22 4 k 4k 0
4 16k 2 0
1
k
2
4
27. c) kx 2 2 x 4k 0 have real roots
real roots occur when 0
i.e. 22 4 k 4k 0
4 16k 2 0
1
k
2
4
1 1
k
2 2
28. c) kx 2 2 x 4k 0 have real roots
real roots occur when 0
i.e. 22 4 k 4k 0
4 16k 2 0
1
k
2
4
1 1
k
2 2
(iii ) For what value of a is the line y ax a tangent to
the circle x 2 y 2 20 x 10 y 100 0?
29. c) kx 2 2 x 4k 0 have real roots
real roots occur when 0
i.e. 22 4 k 4k 0
4 16k 2 0
1
k
2
4
1 1
k
2 2
(iii ) For what value of a is the line y ax a tangent to
the circle x 2 y 2 20 x 10 y 100 0?
x 2 a 2 x 2 20 x 10ax 100 0
30. c) kx 2 2 x 4k 0 have real roots
real roots occur when 0
i.e. 22 4 k 4k 0
4 16k 2 0
1
k
2
4
1 1
k
2 2
(iii ) For what value of a is the line y ax a tangent to
the circle x 2 y 2 20 x 10 y 100 0?
x 2 a 2 x 2 20 x 10ax 100 0
a 2
1 x 2 10 2 a x 100 0