# Solving Log Eqns Simultaneously

4 replies to this topic

### #1 nitrous

nitrous

Newbie

• Members
• 1 posts

Posted 06 March 2008 - 12:34 PM

Hey guys/and girls

I have a problem with solving logarithmic equations simultaneously with my Classpad. I'm using 3.02 OS.

When I try to solve the?following eqations simultaneously:

0 = A ln(4-B )
18 = A ln(6-B )

I can't seem to get a useful?decimal answer...

I tried solving them both going throgh Action>Advanced>Solve and using the simultaneous equation solving function in 2D.

Any help will be greatly appreciated. Thanks in advance

Newbie

• Members
• 17 posts
• Gender:Male
• Location:Teesside, UK
• Interests:music<br />comedy<br />drama<br />physics<br />maths<br />GNU/Linux

• Calculators:
casio FX - 85ES
casio FX 991ES
Texas TI-83 Plus Silver edition
casio FX-7400G+

Posted 09 March 2008 - 09:47 PM

first of all, I don't know why the classpad shouldn't be able to solve this, but I think the advanced> solve command is meant for single equations, not simultaneous?? I'm not sure about this, I don't often use the CP to solve them.

Second of all, isn't this a trivially easy case to be bringing the full might of a CAS to bear on? If you look at the first equation it's clear that either A must be 0, or ln(4- must be 0. Since A cannot be 0 otherwise it would invalidate the second equation, then B must be 3.
Rearrange the second equation with B=3, and you get the answer for A....

I think it's probably quicker that way than to bother to type it into any computer :-)

### #3 Behnoud

Behnoud

Casio Technician

• Members
• 338 posts
• Gender:Male
• Location:Iran

• Calculators:
CP 300+ OS2.2/
FX 3600 pv/
FX 115 s/
FX 602P

Posted 10 March 2008 - 09:08 PM

I'm here just to say an unrelated observation:
Solving "~=e^(~)" take more time than "Ln(~)=~"!

### #4 ECE

ECE

Casio Freak

• Members
• 152 posts
• Gender:Not Telling
• Location:USA

• Calculators:
fx-CG20 o.s1.04
fx9860GII SD o.s2.00
fx9860G Slim o.s1.10
fx9860GSD o.s2.01 (GII hacked)
Algebra FX2.0 Plus
CFX9850GBplus
fx5800p
fx3650p
fx570ES Plus
EA-200 Casio Data Analyzer

Posted 12 March 2008 - 11:18 AM

Hey guys/and girls

I have a problem with solving logarithmic equations simultaneously with my Classpad. I'm using 3.02 OS.

When I try to solve the following eqations simultaneously:

0 = A ln(4-B )
18 = A ln(6-B )

I can't seem to get a useful decimal answer...

I tried solving them both going throgh Action>Advanced>Solve and using the simultaneous equation solving function in 2D.

Any help will be greatly appreciated. Thanks in advance

hello,
the new O.S v.3.03 solves this type of problems,
type: solve({A*ln(4-B=0,A*ln(6-B=18},{A,B})
you will get the ans.
{A=18/ln(3), B=3}.

### #5 Behnoud

Behnoud

Casio Technician

• Members
• 338 posts
• Gender:Male
• Location:Iran

• Calculators:
CP 300+ OS2.2/
FX 3600 pv/
FX 115 s/
FX 602P

Posted 12 March 2008 - 02:29 PM

It's a great improvement!
Well done CASIO!

#### 0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users