mersenneforum.org  

Go Back   mersenneforum.org > Extra Stuff > Miscellaneous Math

Closed Thread
 
Thread Tools
Old 2021-01-04, 12:46   #1
drmurat
 
"murat"
May 2020
turkey

3×29 Posts
Default Calculation

C = a x b +a + b
İf we know c how can we calculate a and b
For example
120 = 10 x 10 + 10 + 10

Last fiddled with by drmurat on 2021-01-04 at 12:53
drmurat is offline  
Old 2021-01-04, 12:48   #2
LaurV
Romulan Interpreter
 
LaurV's Avatar
 
Jun 2011
Thailand

23·19·61 Posts
Default

We can not.
If we could, factoring would be a breeze.
LaurV is offline  
Old 2021-01-04, 13:32   #3
retina
Undefined
 
retina's Avatar
 
"The unspeakable one"
Jun 2006
My evil lair

2×3×1,013 Posts
Default

Quote:
Originally Posted by drmurat View Post
C = a x b +a + b
İf we know c how can we calculate a and b
For example
120 = 10 x 10 + 10 + 10
The solution is not unique.

e.g. We can always set a=0 and b=C.
retina is offline  
Old 2021-01-04, 13:36   #4
Dr Sardonicus
 
Dr Sardonicus's Avatar
 
Feb 2017
Nowhere

25·33·5 Posts
Default

Quote:
Originally Posted by drmurat View Post
C = a x b +a + b
İf we know c how can we calculate a and b
<snip>
By factoring C + 1.

C = a*b + a + b

C + 1 = a*b + a + b + 1

C + 1 = (a + 1)*(b + 1)

Dr Sardonicus is offline  
Old 2021-01-04, 13:45   #5
drmurat
 
"murat"
May 2020
turkey

1278 Posts
Default

Quote:
Originally Posted by Dr Sardonicus View Post
By factoring C + 1.

C = a*b + a + b

C + 1 = a*b + a + b + 1

C + 1 = (a + 1)*(b + 1)

İf

C = 2*a*b + a + b
Or
C = 3*a*b + a + b

MODERATOR NOTE:

Given the equation

C = k*a*b + a + b

there is an obvious algebraic factorization similar to the one I provided above.


Thread closed.

Last fiddled with by Dr Sardonicus on 2021-01-04 at 13:59 Reason: Notification of thread closure
drmurat is offline  
Old 2021-01-06, 11:15   #6
drmurat
 
"murat"
May 2020
turkey

3×29 Posts
Default Any algebria book suggestion

Okay I Must solve a equation
Think that the equation
a>0 b>0 a, b integer
10 * a * b + a + b = c
İn this forum I learned
a x b + a + b + 1 = c + 1
( a + 1 ) x ( b + 1 ) = c + 1

Now the equation is
9 x a x b + ( a + 1) x ( b + 1 ) = c + 1

İt is still hard
Also I know
(5 x a + ... ) x ( 2 x b + ... ) =c + ...

Any book sugestion ?

MODERATOR NOTE: Thread merged with earlier "Calculation" thread.

Last fiddled with by Dr Sardonicus on 2021-01-07 at 14:29 Reason: As indicated
drmurat is offline  
Old 2021-01-07, 13:48   #7
BudgieJane
 
BudgieJane's Avatar
 
"Jane Sullivan"
Jan 2011
Beckenham, UK

F016 Posts
Default

I wouldn't call this an equation, because if you reverse it it becomes an instruction for calculating c given a and b.

c = 10ab + a + b

so there is an infinite number of "solutions".

a=b=0 gives c=0
a=b=1 gives c=12
a=0 b=1 or a=1 b=0 gives c=1
and so on ad infinitum.

In my humble opinion, you do not need a book on algebra to work this out.
BudgieJane is offline  
Old 2021-01-07, 14:23   #8
Viliam Furik
 
"Viliam Furík"
Jul 2018
Martin, Slovakia

1011111002 Posts
Default

Quote:
Originally Posted by BudgieJane View Post
I wouldn't call this an equation, because if you reverse it it becomes an instruction for calculating c given a and b.
Why not? Equations can have an infinite number of solutions.

And for drmurat:

k * a * b + a + b = c
k^2 * a * b + k * a + k * b = k * c
k^2 * a * b + k * a + k * b + 1 = k * c + 1
(k * a + 1) * (k * b + 1) = k * c + 1
Viliam Furik is online now  
Closed Thread

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wrong GHz Calculation? mPat PrimeNet 2 2017-06-24 18:04
MOD calculation / reversing radugafener Math 5 2015-02-12 15:41
Primorial calculation FreakyPotato Programming 7 2015-02-06 10:33
GHZ-days calculation Q tcharron PrimeNet 4 2014-06-27 23:27
mod p calculation help kurtulmehtap Math 3 2010-10-11 15:02

All times are UTC. The time now is 20:16.

Sun Feb 28 20:16:22 UTC 2021 up 87 days, 16:27, 0 users, load averages: 3.60, 3.39, 3.29

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.