# Thread: to find the x value... i just wonder why the two exponents are not the same.

1. ## to find the x value... i just wonder why the two exponents are not the same.

to find the x value... i just wonder how to find the x since the two exponents are not the same.

5x^7+3x^4=242
5x^7+3x^4-242 = 0
i could not factor it ...

have some help.

2. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Try x=1, then x=2:
at least you'll see there's a solution >1 and <2

3. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Thank you Sir Denis... How did you solve it sir... please can you show the solution sir?

5(1)^7+ 3(2)^4
5(1)+3(16)
5+48
=53... it isnot 242.... ������

4. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Originally Posted by rcs
Thank you Sir Denis... How did you solve it sir... please can you show the solution sir?

5(1)^7+ 3(2)^4
5(1)+3(16)
5+48
=53... it isnot 242.... ������
this has to be solved using numeric methods.

The only real solution is

$x \approx 1.71275$

There are 3 complex conjugate pair solutions as well.

5. ## Re: to find the x value... i just wonder why the two exponents are not the same.

How is it done sir?
Is it done by simply pluggig in any values of x element of N or Z?
That takes time sir

6. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Oh My God. Is there any help i can have in here?

7. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Originally Posted by romsek
this has to be solved using numeric methods.

The only real solution is

$x \approx 1.71275$

There are 3 complex conjugate pair solutions as well.
How come sir? How is it done :-(

8. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Originally Posted by rcs
How come sir? How is it done :-(
https://en.wikibooks.org/wiki/Numeri...uation_Solving

9. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Originally Posted by rcs
Oh My God. Is there any help i can have in here?
That is totally uncalled for. It is rude and off-putting.
You have posted here many many times. Are you too lazy to use available web-based calculators.?

10. ## Re: to find the x value... i just wonder why the two exponents are not the same.

I suspect the OP is frustrated because his follow up question is not understood. He wants to know analytically how Denis found that a solution lies between 1 and 2.

There is no mechanical trick. Even if Denis did not graph the function, he undoubtedly observed that for non-negative values of x

$f(x) = 5x^7 + + 3x^4$ increases rapidly and monotonically from a value of zero at x = 0.

It is also obvious by inspection that f(1) = 8 and f(3) >> 400. So if there is an integer solution, it must be 2. But f(2) is too large.

Thus, there is a positive solution between 1 and 2.

11. ## Re: to find the x value... i just wonder why the two exponents are not the same.

Originally Posted by Plato
That is totally uncalled for. It is rude and off-putting.
You have posted here many many times. Are you too lazy to use available web-based calculators.?
Sorry Sir Plato... i dont understand you ...just Chill

I just wanted to see whether this is doable or solvable algebraially... for me it is seemed not...