This question is C1 January 2006, Q10 part (d), for reference.
I got to k^(2)<12, and then k<=+/-2root3. I thought I should leave the answer as k<2root3, as k<-2root3 is inclusive in k<2root3.
The answer is -2root3<k<2root3, and I am not sure why. Could somebody explain please?
C1 Solving inequalities exam question - help please Watch
- Thread Starter
- 04-04-2016 15:53
Last edited by B_9710; 04-04-2016 at 16:06.
- 04-04-2016 16:05
- 04-04-2016 16:09
It is k>-2root3 as the square of (-2root3) is 12. If we make it more negative then k^2 will be greater than 12.
Posted from TSR Mobile
- 04-04-2016 16:45
I loved your explanation (http://www.wolframalpha.com/input/?i=plot+y%3Dx%5E2-12)
It is like finding the roots of X^2-12=0
Generally I try remembering that
(Original post by B_9710)
Thing about the graph of , to satisfy the inequality (replacing k with x) the curve must be below the x axis so that y<0.
You cannot just square root it when there is an inequality. By your logic -10 should satisfy the inequality, but does it in reality? No.
Last edited by Zacken; 04-04-2016 at 20:47.
- 04-04-2016 19:04