## louis413 3 years ago 2(x-1)^3=x+1

1. lgbasallote

hmm okay?

2. louis413

can u solve it?

3. louis413

???

4. lgbasallote

solve for x?

5. louis413

yeah

6. lgbasallote

here's my thought let x - 1 = a therefore a +1 = x 2a^3 = a + 1 + 1 2a^3 = a + 2 2a^3 - a - 2 = 0 does that give you any ideas?

7. louis413

2(x-1)^3=x+1 noo sorry not really can u tell me how to do it just by factoring etc?

8. lgbasallote

lol that's what im thinking too

9. lgbasallote

@myininaya pls help here

10. myininaya

Hey @lgbasallote what was wrong with your way?

11. myininaya

It seems to be awesome! :)

12. lgbasallote

i don't know what to do next lol

13. myininaya

Try doing a little of testing possible rational zeros for what you have

14. myininaya

Synthetic division will come in handy

15. lgbasallote

you heard her @louis413 ;)

16. louis413

lol im only in alg/trig in high schooll.. loll wut is that?

17. myininaya

oh wait i think i made a mistake anyways... let me try again but yeah that is what i would do test to see if any possible rational zeros work

18. myininaya

algebra/trig? which one?

19. louis413

well im takling the algebra2/trig course right now at summer school

20. myininaya

synthetic division and looking at possible rational zeros are in algebra

21. myininaya

ok so what have you learned then?

22. louis413

factoring... quadratic formula completeing the squares etc

23. myininaya

And is your equation written correctly?

24. louis413

yes can it be solved like 2(x-1)^2(x-1)-1(X-1)=0

25. myininaya

I can only see to find a real approximation by looking at the graph and seeing where it crosses the x-axis

26. shubhamsrg

would you like to go for a trignometric solution? might seem complicated but is easy.. involves inverse function just a bit..and sin 3x etc formullas ?

27. shubhamsrg

well.. in 2a^3 - a - 2 = 0 let a = m sin y => 2m^3 sin^3 y - msin y -2 =0 multiplying both sides by (-2/m^3) => -4sin^3 y + 2sin y/(m^2) + 4/(m^3) =0 our aim is to convert this in the form of -4sin^3 y + 3 siny which will convert it into sin 3y and simplify things we have to chose a particular value of m for that purpose in our case 2/m^2 = 3 or m = sqrt(3/2) and -sqrt(3/2) thus we have these 2 eqns : -4sin^3 y + 3sin y + 8sqrt(2)/(3sqrt(3)) = 0 and -4sin^3 y + 3sin y - 8sqrt(2)/(3sqrt(3)) = 0 => sin 3y = - 8sqrt(2)/(3sqrt(3)) and =>sin 3y = 8sqrt(2)/(3sqrt(3)) now using any scientific calculator, we may find value of y,then a(=msin y) and then finally x(=a+1)

28. shubhamsrg

hope i was able to explain well..