solve 0.5=(3k)/(3k+9)*(k*sqrt(8))/(k*sqrt(8)+8)*(k*sqrt(7))/(k*sqrt(7)+7)*(k*sqrt(6))/(k*sqrt(6)+6)*(k*sqrt(5))/(k*sqrt(5)+5)*(2k)/(2k+4)*(k*sqrt(3))/(k*sqrt(3)+3)*(k*sqrt(2))/(k*sqrt(2)+2)*k/(k+1)