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Find all real numbers x such that
(3^x - 27)^3 + (27x - 3)^3 = (3x + 27x - 30)^3

 Nov 27, 2022
 #1
avatar+307 
-2

Find all real numbers x such that

(3x27)3+(27x3)3=(3x+27x30)3

well, this is going to be a pain to expand, but i see no other way... Oh god.

Okay after 30 minutes of backbending expanding, i got this:

27x92+x+3x+719683+19683x36561x2+729x27=27000x381000x2+81000x27000

yeah.... thats, quite a bit of math. Now lets simplify! YAY! *sigh..*

27x92+x+3x+77317x3+74439x2+80271x=0

Im acually having fun doing this! No sarcasm like acually!

Okay lets acually do it another way.

[(3x27+27x3)][(3x27)2(3x27)(27x3)+(27x3)2]=27000x381000x2+81000x27000

(30x30)[(3(x9))2(3(x9)3(9x1))+(3(9x1))2]=thethingidontwannawrite

(30x30)[9(x218x+81)(9(9x282x+9))+(9(81x218x+1))=againidontwannawriteit

9(30x30)[x218x+819x2+82x9+81x218x+1]=yeahyeahyeah

270(x1)[73x2+46x+73]=ohgod

the discriminant of [73x2+46x+73]is negative, so it has no real roots, just saying, you know.

so basically 270(x1)=(30x30)3

more simplifying....

270(x1)=270(100x3300x2+300x100)

x1=100x3300x2+300x100

100x3300x2+299x99=0

i think ill let you take it from here

Note: I've spent more than an hour on this prob, but i haven't solved it yet, anybody that can give the solution i will appreciate it

 Nov 27, 2022
 #2
avatar+307 
-2

can anybody online check my work? My brain is damaged.

Where do i go? to the left, where nothing is right, or to the right, where nothing is left?

 Nov 27, 2022
 #3
avatar+33654 
+1

Here is my approach:

 

 Nov 28, 2022
 #4
avatar+307 
-2

Ahh i see... thank you for clarifying, i understand perfectly now

 Nov 29, 2022

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