Maths Q7 c (1 Viewer)

[donrob15]

part i was easy finding the descriminant
how do you do part ii? i ad some i dea but couldnt actually put down an answer. i mey need to know this for extension 1 so any help would be appreciated.

 

[JJPH]

What was the actual question, im pretty blurred out.

Something to do with K, parabola and not intersecting 2x - 1 or something?

 

[earthnfire]

part i was easy finding the descriminant
how do you do part ii? i ad some i dea but couldnt actually put down an answer. i mey need to know this for extension 1 so any help would be appreciated.

I'm pretty sure my answer is right. I wrote:

ab = c/a = 1

as: ab=1
b= 1/a
Therefore a + 1/a is the same as a + b = 3
So a + 1/a = 3

Hope this helps...goodluck with the rest of your exams.

 

[chainedchaos]

Where y=2x^2 +kx + 9 does NOT intersect with y=2x + 1:

2x^2 +kx + 9 (is not equal to sign) 2x +1

then you just rearrange it to get 2x^2 +(k-2)x + 8 which is now not equal to zero. So you put the discriminant(from i) < 0 because there are no real roots.
Then you cansolve the inquality like any other quadratic inequality

 

[earthnfire]

Lol...soz...i just realised i answered the wrong question...i answered 7a. I can't help you with 7c...i had the same trouble as you...lol

but goodluck with ur other exams anyway

 

[shinji]

oh, this is easy. lol

just wats it me called ..... solve them simulataneously

and then u should get a similar equation to the one in part II or sumin
and then u use the discriminate equation from part I or watever
and then u just make it less than 0 ~~

 

[donrob15]

i figured it out

you let the straight line = the parabola in part 2. you make it all = 0 and you end up getting the discriminant you found in part i. the discriminant has to be <0 for it to not intersect the st line. solve x for discriminant<0. i got -6<k<10. i only wish i knew that in the test.

 

[Benmc]

Yeah i got the two K values but i didn't know the equation had already gotten the curves/ lines merged together.

There i skipped it and didn't bother completing and just had the stupid k values. I knew it was going to be an inequality but i thought i had to rewrite the equation for the two lines to be solved, but it was already fcuking rewritten. BOS could have said that. Bastards

 

[s2indie]

Dammit. I was practically there! Just didn't pen it down.