Question 61638
It's useful to know in general that {{{(a+bi)(a-bi) = a^2-abi+abi-(b^2)(i^2) = a^2-(b^2)(-1) = a^2+b^2}}}.

Apply this to {{{((x-1)+5i)((x-1)-5i)}}} where a=(x-1) and b=5
and you get: {{{(x-1)^2+5^2 = x^2-2x+1+25 = x^2-2x+26}}}.