you will find the problem in project Euler.net.

Because the formula I used is - so I think - not obvious, here is its development:

b = blue disks

a = amount od blue and red disks

b/a * (b-1)/(a-1) = 1/2

b^2 - b = a^2- a/ 2

b^2 - b +(1/2)^2 = a^2 - a/2 + 1/4

(b-1/2)^2 = (2*(a^2 - a) + 1)/4

b = sqrt(2*(a^2 - a) + 1)/2 + 1/2

b = (sqrt(2(a^2 - a)+1)/2

It looks like that it could work. But to my disappointment the solution is not correct.

Can anybody help me?

greetings

Volker

Because the formula I used is - so I think - not obvious, here is its development:

b = blue disks

a = amount od blue and red disks

b/a * (b-1)/(a-1) = 1/2

b^2 - b = a^2- a/ 2

b^2 - b +(1/2)^2 = a^2 - a/2 + 1/4

(b-1/2)^2 = (2*(a^2 - a) + 1)/4

b = sqrt(2*(a^2 - a) + 1)/2 + 1/2

b = (sqrt(2(a^2 - a)+1)/2

It looks like that it could work. But to my disappointment the solution is not correct.

Can anybody help me?

greetings

Volker

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