Question

Find the interval in which k shuld lie so that the roots of the equation 2x^2-kx + 8 =0 are b/w -1 and 4

Answer 1

(x-a) (x-b)=0
x^2 -(a+b) x + ab =0
2x^2 - 2(a+b) x + 2ab =0

=> 2(a+b) =k and => 2ab=8

Answer 2

I think..i Did nt get u...

Answer 3

Let a and b be the roots of 2x^2-kx + 8 =0

Answer 4

Now u got it?

Answer 5

Ok...So..Hw to Find the Interval

Answer 6

=>2ab =8
(-1<=a<=4 and -1<=b<=4)

Answer 7

=> 2(a+b) =k
4(a+b)^2 =k^2
4a^2 + 8ab + 4b^2 =k^2
4a^2 + 24 + 4b^2 =k^2
k^2 =4a^2 +4b^2 +24

Answer 8

Now find the max value of k and minimum value of k

Answer 9

play around these.