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(1-2a)^2/6-a^2-(14-a^7)/3

 Sep 6, 2015

Best Answer 

 #6
avatar+980 
+5

EDIT: Woops Dragonlance is correct my answer should go like this. 

 

4a24a+16a228+2a7=0

 

2a72a24a=27

 

Or is the general form this?

 

2a72a24a27=0

 

 

 

On a different note can you still edit your previous posts? 

 Sep 8, 2015
 #1
avatar
0

(1-2a)^2/6-a^2-(14-a^7)/3,

 

After a number of algebraic steps you get:

 

a =1.521282721...........etc., which is the right answer.

 Sep 7, 2015
 #2
avatar+980 
0

Assuming it is equal to 0...

 

(12a)2/6a2(14a7)/3=0

 

(12a)(12a)/6a2(14a7)/3=0

 

(4a24a+1)/6a2(14a7)/3=0

 

4a24a+16a22(14a7)=0

 

4a24a+16a2282a7=0

 

2a7+2a2+4a=27

 

... but from here I'm not sure what to do

 Sep 7, 2015
 #3
avatar+1316 
0

 

Expand


(12a)26a214a73

 

Find common denominator. it is 6

 

2(a7+14)66a26+(2a+1)26

 

 

2(a7+14)6a2+(2a+1)26

 

Expand this part

 

(2a+1)2

to this

4a24a+1

then expand this

2(a7+14)

to this

2a728

then combine the parts

2a76a2+4a24a+128

simplefy it and put it over the 6 and make equal to 0

2a72a24a276=0

change to this

2a72a24a6=276

change to this

2a72a24a=27

 

I out of time. Next post I solve it (or try to).

 Sep 7, 2015
 #4
avatar+1316 
0

This is strange. This question do not show on the question page but it do show on the answer page. Do any one know why?

 

Any way, I play with this for a long time and I still not know how to solve it.

I plug both the first equation and then mine into Wolframalpha and it give a=1.52128... 

so I know I do the rearranging correctly but I still not know the steps to get to the answer.

 

If one of the mods would do it that it would be great because I would like to know how.

 Sep 7, 2015
 #5
avatar+980 
0

ha we both got to the same point and couldn't do it :)

Polynomials comes to mind but I haven't learnt that yet.

 Sep 8, 2015
 #6
avatar+980 
+5
Best Answer

EDIT: Woops Dragonlance is correct my answer should go like this. 

 

4a24a+16a228+2a7=0

 

2a72a24a=27

 

Or is the general form this?

 

2a72a24a27=0

 

 

 

On a different note can you still edit your previous posts? 

zacismyname Sep 8, 2015
 #7
avatar+1316 
0

It is a degree 7 polynomial so there are 7 solutions for it. It is a odd degree so at least 1 solution is a real number. This is the number wolfram give.

 

I think the way this is solved is with the bisection method. It look easy to do, but graphing it look even easier. I already do that but it only give the answer to 1 decimal place.

 

 

----------

 After a short time or if someone make another post then there do not seem to be a way to edit an older post.

 Sep 8, 2015

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