Integrate the function (3x+4)^2 using methods of expansion and substitution

For expansion:(3x+4)²=9x²+24x+16, go through expansion in online classroom. Now we integrate this using standard polynomial integration rules.
For substitution:
use the substitution u=3x+4, and use the integration by substitution variable change formula; dx=(dx/du)du. Rearrange substitution above to find du/dx=1/3, now integrate obtained function u²/3 using standard polynomial integration rules.