
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
December 3rd, 2017, 02:31 PM  #1 
Newbie Joined: Dec 2017 From: USA Posts: 3 Thanks: 0  Finding the value of A and b from a log graph.
This is the question in my book: https://image.prntscr.com/image/eoWE...tBk7l6Z6WQ.png I made on paint how far I got so far. However I'm having trouble with the last 23 questions. I believe "A'' is 1,9 because for the differential equation I took: 0,740,175 = 0,565 and 0,0030,298 = 0,298 and 0,565/0,298 = 1,9 However, can someone verify that that's correct? And if someone could help me with the other two, I'll very much appreciate it. Thank you. Last edited by skipjack; December 3rd, 2017 at 02:57 PM. 
December 3rd, 2017, 03:10 PM  #2 
Global Moderator Joined: Dec 2006 Posts: 19,870 Thanks: 1833 
Is 0,45 in the table supposed to be 0,55? Were you given the table or the graph? Your equation "0,0030.298 = 0.298" should be "0,003  (0.295) = 0.298". Try to be consistent with the variable names... is it U or V, a or A, b or B? I would think that A = 1,9 is close enough. The value of B should be slightly less than 0,74 (anything from 0,734 to 0,737 would be acceptable). Last edited by skipjack; December 3rd, 2017 at 03:38 PM. 
December 3rd, 2017, 03:24 PM  #3 
Newbie Joined: Dec 2017 From: USA Posts: 3 Thanks: 0 
Yes, 0,55 my apologies. I was given the nonlog table V, 1.5 2,5 3,5 4,5 5,5 I, 0,51 0,66 0,79 0,9 1,005 Last edited by skipjack; December 3rd, 2017 at 04:03 PM. 
December 3rd, 2017, 04:05 PM  #4 
Global Moderator Joined: Dec 2006 Posts: 19,870 Thanks: 1833 
There are minor inaccuracies in your log table. Were you told to use logs?

December 3rd, 2017, 04:18 PM  #5  
Newbie Joined: Dec 2017 From: USA Posts: 3 Thanks: 0  Quote:
Yes. We got a standard table. Turn it into log. Draw a graph, put the dots on it, and then solve for A and B to make the formula U = b*I^a, so all I need is A and b. Last edited by skipjack; December 4th, 2017 at 01:43 PM.  
December 4th, 2017, 03:06 PM  #6 
Global Moderator Joined: Dec 2006 Posts: 19,870 Thanks: 1833 
Having found a = 1.9 correctly, b = 0.74  1.9*0.003 = 0.7343. Using b = 0.175 + 1.9*0.295 would give about the same result, especially if you hadn't rounded up the logarithms. 

Tags 
finding, graph, log 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Finding the length of a graph (polar)  eglaud  Calculus  3  May 4th, 2016 06:26 PM 
Finding point in graph  Mrto  Calculus  1  April 25th, 2016 09:45 PM 
Finding c from graph  chocolate  Algebra  2  July 2nd, 2012 04:02 AM 
Finding a polynomial function given a graph  ckooiker  Algebra  2  September 22nd, 2011 04:49 PM 
Finding the function of this graph  laku  Algebra  1  January 31st, 2011 06:13 PM 