Question

It is given that the difference between the zeros of 4x^2 -8kx+9 is 4 and k>0.Find the value of k.

Answer 1

let the zeroes be a and b
a - b = 4
a + b = 2k
ab = 9/4
(a - b)^2 = (a + b)^2 - 4ab
16 = 4k^2 - 9
k^2 = 25/4
k = 5/2 or -5/2
since k is greater than 0 so
k = 5/2

It doesn't not matter whether you take a - b or a + b in this question particularly as we have to square it in further steps but for other questions we need to take separate cases for difference of the roots because we don't know which one is greater.
Hope this helps!!!!!

Answer 2

Hope it will be helpful to you