Question

correction:

9/25(u+7)u^11 du =

9/25(u^12 + 7 u^11) du

and you can easily integrate this

indefinate integral of 9x(5x-7)^11 dx

using the u substitution method:
i know u= (5x-7) but when i use this the x in the 9x doesn't cancel thus x= (u+7)/5. however when i put this in the equation i have trouble getting the answer. please help.

9x(5x-7)^11 dx =

9/5(u+7)u^11 dx/du du =

9/25(u+7)u^11 du

Note that dx/du = 1/5.

9/25(u+7)u^11 du =

9/25(u^12 + 7 u^11)