FlyinSolo_424 3 years ago Find the value of x: 2x^3 - 5x^2 - x + 20 = 0

1. Aryang

would you like to go for a trignometric solution ?

2. FlyinSolo_424

I just need the value of x :o the answers have 2 x values. Its a whole different equation but Ive added everything and I just needed help on finding the x values of this because It confused me

3. shubham.bagrecha

what is the ans.?

4. Aryang

if you want soln,,i can provide hint : see shubhamsrg's soln : http://openstudy.com/users/shubhamsrg#/updates/4fed5f8ae4b0bbec5cfcc1ac

5. Aryang

first you have to convert the eqn into depressed but..

6. FlyinSolo_424

1: x= -4/3, x= -5 2: x= -4/3, x= 5 3:x= 4/3, x= -5 4:x= 4/3, x= 5

7. shubham.bagrecha
8. FlyinSolo_424

I tried plugging it into wolframalpha already.. didnt work -_-

9. shubham.bagrecha

didn't work! there the ans. given is -1.6

10. FlyinSolo_424

Ok that gives me one answer but :o

11. FlyinSolo_424

I guess ill just try Plugging 5 and negative 5 into the original thing.. Thanks :p

12. FlyinSolo_424

Wait can Someone actually Help me? Cause Ive tried plugging the two 5's in but Its not equaling out. @Wired @JohnHanShanghai , the original equation is this,

13. FlyinSolo_424

|dw:1342092140095:dw|

14. shubham.bagrecha

have you tried 2 and minus 2?

15. FlyinSolo_424

But thats not a possible answer?

16. FlyinSolo_424

I think Im retarded because either 5 or -5 have to work . But I tried and of course I did something wrong

17. Wired

Wolfram says -4/3 and 5. Must've done something wrong when solving the equation.

18. FlyinSolo_424

there are 2 answers with -4/3

19. FlyinSolo_424

Wait where does it say 5?

20. Wired
21. FlyinSolo_424

Well I didnt put int he original equation but thank you ! Again lol (:

22. shubham.bagrecha

The correct eq. is 3x^2-11x-20=0

23. Wired

$\frac{2}{x-2}+\frac{7}{x^{2}-4}=\frac{5}{x}$ $\frac{x+2}{x+2}*\frac{2}{x-2}+\frac{7}{x^{2}-4}=\frac{5}{x}$ $\frac{2x+4+7}{x^{2}-4}=\frac{5}{x}$ $2x^{2}+11x = 5x^{2}-20$ $3x^{2}-11x-20 = 0$

24. Wired

When in doubt, go back to the beginning :)

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