Answer:
[tex]48x^9-72x^7+36x^5[/tex]
Step-by-step explanation:
The initial expression is:
[tex]9x^5+3x(4x^4-3x^2)^2[/tex]
First expand the squared part (inside the parenthesis):
[tex]9x^5+3x(4x^4-3x^2)(4x^4-3x^2)\\9x^5+3x(16x^8-24x^6+9x^4)\\[/tex]
Then, multiply the terms inside the parenthesis by 3x applying the distributive property:
[tex]9x^5+3x(16x^8-24x^6+9x^4)\\9x^5+48x^9-72x^7+27x^5[/tex]
Finally add terms with the same exponent
[tex]48x^9-72x^7+36x^5[/tex]
