(a^2+b^2+2ab)+(2ac+2bc)+c^2=(a+b)^2+c(2a+2b+c)
=(k+1+k+3)^2+(4-2k)[2(k+1)+2(k+3)+(4-2k)]
=(2k+4)^2+(4-2k)(12+2k)
=64