Chapter 5 - Section 5.3 - Special Products - Exercise Set - Page 368: 79

$4-12x^5+9x^{10}$

Using $(a\pm b)^2=a^2\pm2ab+b^2$ or the square of a binomial, the square of the given expression, $ (2-3x^5)^2 ,$ is \begin{array}{l}\require{cancel} (2)^2-2(2)(3x^5)+(3x^5)^2 \\\\= 4-12x^5+9x^{10} .\end{array}