in the original version, I'd say there is no trial and error required at all. Looking at the bottom box, x^2+x should be at most 24, so x<5 and (x^2+x) + (x+5) should be at least 21, so x>3. Now you found x.
In the second version, first of all, I wouldnt guess I have to try and find the centre digit, and secondly it isnt obvious to me, how I could find it, even now that you pointed out I should try and find it (and knowing what it should be from the other version). So I like the original better^^
Edit:I guess I see what you want in the second maybe? If I do law of leftowers on the two diagonals with the blue lines, I can find the sum of the two diagonals withoutthe center and subtracting the square diagonally above the center once. That gives me the sum of the centre square and the one diagonally above. Is that the intended way to start? Still dont know how to isolate the centre digit though. Edit 2: The first number I find with this method was the bottom right number in the centre box
. I can see now that I should have just looked at one diagonal and then when I find the center with that, start looking at the other diagonal. I was looking at both diagonals together and then looked at the result (which was sum of two numbers, to compare with the that diagonal, but that gave me the 1 first, which in turn gives an 8 above it. the center 4 is still not clear to me). I kept solving now, found the center as my fifth digit (using sukoku on the 6s to resolve the sum of 10 I mentioned first).
In the second version, first of all, I wouldnt guess I have to try and find the centre digit, and secondly it isnt obvious to me, how I could find it, even now that you pointed out I should try and find it (and knowing what it should be from the other version). So I like the original better^^
Edit:I guess I see what you want in the second maybe? If I do law of leftowers on the two diagonals with the blue lines, I can find the sum of the two diagonals withoutthe center and subtracting the square diagonally above the center once. That gives me the sum of the centre square and the one diagonally above. Is that the intended way to start? Still dont know how to isolate the centre digit though. Edit 2: The first number I find with this method was the bottom right number in the centre box
. I can see now that I should have just looked at one diagonal and then when I find the center with that, start looking at the other diagonal. I was looking at both diagonals together and then looked at the result (which was sum of two numbers, to compare with the that diagonal, but that gave me the 1 first, which in turn gives an 8 above it. the center 4 is still not clear to me). I kept solving now, found the center as my fifth digit (using sukoku on the 6s to resolve the sum of 10 I mentioned first).