Chapter 5 - Section 5.3 - Special Products - Exercise Set - Page 368: 80

$4-12x^6+9x^{12}$

Using $(a\pm b)^2=a^2\pm2ab+b^2$ or the square of a binomial, the square of the given expression, $ (2-3x^6)^2 ,$ is \begin{array}{l}\require{cancel} (2)^2-2(2)(3x^6)+(3x^6)^2 \\\\= 4-12x^6+9x^{12} .\end{array}