what is [(d+9) ​7 ] 3 equal to?

OK....if you really want to know.....

[(d + 9)^7]^3  =  (d + 9)^21  =

d^21 + 189 d^20 + 17010 d^19 + 969570 d^18 + 39267585 d^17 + 1201588101 d^16 + 28838114424 d^15 + 556163635320 d^14 + 8759577256290 d^13 + 113874504331770 d^12 + 1229844646783116 d^11 + 11068601821048044 d^10 + 83014513657860330 d^9 + 517244277406668210 d^8 + 2660113426662865080 d^7 + 11172476391984033336 d^6 + 37707107822946112509 d^5 + 99812932472504415465 d^4 + 199625864945008830930 d^3 + 283678860711328338690 d^2 + 255310974640195504821 d + 109418989131512359209

Messy, huh ???