Determine the value(s) of 'K' that will give (k-1)x^2-5x + 10= 0 two imaginary roots.

k so the thing I know is that the discriminant is d<0
so do I solve for k?

I know I would use this formula:
b^2-4ac but how would I get into a formula I can work with would I times the x^2 by -1 and k ? I am unsure could you point me in the right direction???? thanks! so much!

Yes, the discriminant b^2 - 4 ac must be <0 for two complex roots. In your case
a = k-1, b = -5 and c = 10, so the requiremens becomes
b^2 - 4 ac = 25 - 40 (k-1) < 0
k-1 < 5/8
k < 1 5/8