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Help with this question, from 2013 C1 jan Exam (aqa)

A curve has equation y=2x^2 - x -1 and a line has equation y=k(2x-3) where k is constant. (x's do not = multiply)

The curve and the line intersect at two distinct points.

i)show that 4k^2 - 20k + 9 > 0

ii) Find the possible values of K.

Could anyone tell me what to do in this question/ answer it for me! (Just got My C1 past paper back and dont know what i did wrong in this question)

Thankyou
Reply 1
Avatar for Tom722
Tom722
Do you know what happens when the curve and the line intersect?
Reply 2
Avatar for Guy96
Guy96
OP
2
Well here is the question in its FULL
A curve has equation y=2x^2 - x -1 and a line has equation y=k(2x-3) where k is constant. (x's do not = multiply)

a) Show that the x-coordinate of any point of intersection of the curve and the line satisfies the equation- 2x^2 - (2k + 1)*x +3k -1 =0

b) The curve and the line intersect at two distinct points.

i)show that 4k^2 - 20k + 9 > 0

ii) Find the possible values of K.
Reply 3
Avatar for Guy96
Guy96
OP
2
Original post by Tom722
Do you know what happens when the curve and the line intersect?


the Full question is above!
Reply 4
Avatar for Albino
Albino
11
Original post by Guy96
the Full question is above!


at intersection y=y1 at\ intersection\ y = y_1
Reply 5
Avatar for Tom722
Tom722
Original post by Guy96
the Full question is above!


Right, I'm guessing you did part a correctly if you omitted it initially. Not sure how much I'm giving away here but for part i) you'd use the quadratic formula and remember that the value of the determinant depends on k, that should get you the inequality.
Reply 6
Avatar for Guy96
Guy96
OP
2
Original post by Tom722
Right, I'm guessing you did part a correctly if you omitted it initially. Not sure how much I'm giving away here but for part i) you'd use the quadratic formula and remember that the value of the determinant depends on k, that should get you the inequality.


I'm sorry, but I am not trying to answer the question I am trying to work out what I did wrong, if you could give me the answer the part b in full it would be very helpful ( so I can compare it to my answer on the past paper, thanks !


Posted from TSR Mobile
Reply 7
Avatar for usycool1
usycool1
19
Original post by Guy96
I'm sorry, but I am not trying to answer the question I am trying to work out what I did wrong, if you could give me the answer the part b in full it would be very helpful ( so I can compare it to my answer on the past paper, thanks !


Posted from TSR Mobile


How about you post your working and then we can tell you where you went wrong? :smile:

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