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Help with C1 Maths Edexcel

Screen Shot 2016-10-06 at 17.41.06.pngI know that if it has real roots the discriminant must be > 0, but the text book says the answer is < or the same as the value of x, help please?
b2−4ac>064−20k>020k<64k<16/5 b^2 - 4ac > 0 \\64 - 20k > 0 \\ 20k < 64 \\ k < 16/5 \\ Not sure what your textbook is on about - maybe we are both missing something?
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jessnoch
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Original post by dfbenjamin
b2−4ac>064−20k>020k<64k<16/5 b^2 - 4ac > 0 \\64 - 20k > 0 \\ 20k < 64 \\ k < 16/5 \\ Not sure what your textbook is on about - maybe we are both missing something?


Yeah I don't get why it's equal to - I'lll have to ask my teacher tomorrow
Original post by jessnoch
Yeah I don't get why it's equal to - I'lll have to ask my teacher tomorrow


Oh you mean that you have k<=16/5? I think that's because you can sometimes consider a double root to be 2 roots instead of 1. I thought you meant the answer was k<=x which would be really confusing!
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jessnoch
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Original post by dfbenjamin
Oh you mean that you have k<=16/5? I think that's because you can sometimes consider a double root to be 2 roots instead of 1. I thought you meant the answer was k<=x which would be really confusing!


Ohhh okay thankyou! :smile:
Original post by jessnoch
Ohhh okay thankyou! :smile:


No problem - check with your teacher tomorrow anyway since it could be a defined thing in your course that you're assumed to know.

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