# Real Roots A Level MathsWatch

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#1
I'm stuck on 11 part b and c. Do you use the discriminate. I tried and got the wrong answer completely.
Last edited by Anonymous_4657; 5 days ago
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5 days ago
#2
What inequality do you get when you use the discriminant?
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#3
b^2 - 4ac > 0

(Original post by ThomH97)
What inequality do you get when you use the discriminant?
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#4
(Original post by Anonymous_4657)
b^2 - 4ac > 0
I tried putting values in but the answer was something completely different.
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5 days ago
#5
(Original post by Anonymous_4657)
I tried putting values in but the answer was something completely different.
What do you get when you sub the values?
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5 days ago
#6
(Original post by Anonymous_4657)
I tried putting values in but the answer was something completely different.
Are you using b is -20cos(theta), a is 1 and ç is 75?
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#7
cos theta > -1/6000
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5 days ago
#8
(Original post by Anonymous_4657)
cos theta > -1/6000
How?
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#9
(1)^2 - 4(-20cos theta) (75) > 0
1 + 6000cos theta > 0
cos theta . -1 /6000
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5 days ago
#10
(Original post by Anonymous_4657)
(1)^2 - 4(-20cos theta) (75) > 0
1 + 6000cos theta > 0
cos theta . -1 /6000
b is -20cos(theta)
a is 1
c is 75
Try again?
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#11
I've got it now!
Last edited by Anonymous_4657; 5 days ago
0
5 days ago
#12
(Original post by Anonymous_4657)
I don't know what I did wrong actually.
it is not
a^2 - 4bc > 0
it is
b^2 - 4ac > 0
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#13
(Original post by mqb2766)
b is -20cos(theta)
a is 1
c is 75
Try again?
Can you help me with another maths question I've posted please?
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