increase in crit equals how much %mainstat?

been trying to figure this out, and i'd rather have it doublechecked, i'm looking for the ratio of %main stat increase to equal an increase in critical damage from 1.65 to 1.8, i'm ignoring secondary stats.

x=main stat
y=amount of potential
z=added potential

this is what i came up with, but for some reason i can't help but feel there's something wrong here:

1.65*(x+x*y)=1.8*(x+x*(y+z))
1.65x+1.65xy=1.8x+1.8x(y+z)
1.65xy=0.15x+1.8x(y+z)
1.65xy-1.8x(y+z)=0.15x
x(-0.15y-1.8z)=0.15x
-y-12z=1
z=(y-1)/12

Where "s" = secondary stat and r = critical hit rate.
(4x(1+y+z)+s)(1+0.65r) = (4x(1+y)+s)(1+0.80r)
z = ((4x(1+y)+s)(1+0.80r)/(1+0.65r) - s)/4x - 1 - y


So for a character with 1000 STR, 100 DEX, 50% STR, 50% Critical Hit Rate
z = ((4000(1+0.50)+100)(1+0.80*0.50)/(1+0.65*0.50) - 100)/4000 - 1 - 0.50

Where "s" = secondary stat and r = critical hit rate.
(4x(1+y+z)+s)(1+0.65r) = (4x(1+y)+s)(1+0.80r)
z = ((4x(1+y)+s)(1+0.80r)/(1+0.65r) - s)/4x - 1 - y


So for a character with 1000 STR, 100 DEX, 50% STR, 50% Critical Hit Rate
z = ((4000(1+0.50)+100)(1+0.80*0.50)/(1+0.65*0.50) - 100)/4000 - 1 - 0.50

making sure, it's (yadda yadda/4000) -1-0.5, correct?

and this is mainly for my DrK, so rate is 100%, but thanks for the "anything works" formula.

making sure, it's (yadda yadda/4000) -1-0.5, correct?

and this is mainly for my DrK, so rate is 100%, but thanks for the "anything works" formula.

Yes. The -1 and -0.50 is subtracting the similar potential, isolating the difference in potential variable, z.

Yes. The -1 and -0.50 is subtracting the similar potential, isolating the difference in potential variable, z.

allrights thank you very much, to excel with this now, much appreciated.