
Linear Algebra Linear Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
November 22nd, 2016, 11:56 PM  #1 
Newbie Joined: Nov 2016 From: London Posts: 2 Thanks: 0  X(AY+B)+CY+D = (aY+b)(cX+d)
How to calculate a,b,c,d as a function of A,B,C,D, where D is_not_equal BC/A ?? Assume X and Y are variables, and A,B,C,D,a,b,c,d are constants. It can be shown easily that A = ac B = bc C = ad D = bd thus A,B,C,D can be calculated from any a,b,c,d. But what if A,B,C,D are known and D isnot BC/A, how to calculate a,b,c,d ? This question has kept me bogged down for a while and it bothers me that I can't solve it. Your help is appreciated. 
November 23rd, 2016, 03:18 AM  #2 
Math Team Joined: Jan 2015 From: Alabama Posts: 3,192 Thanks: 871 
If, as you say, B= bc, C= ad, and A= ac then BC/A= abcd/ac= bd= D. It is impossible to find values of A, B, C, D such that D is not BC/A. The problem you are trying to set up is impossible.

November 23rd, 2016, 07:09 AM  #3 
Newbie Joined: Nov 2016 From: London Posts: 2 Thanks: 0 
I am afraid you are right. Reason I ask is that I have this formula (left side) and I would like to write it in the form of the right side. But apparently, the equation as per the title is only correct if D=BC/A. So, back to the drawing board for me, and find an alternative for the right side that allows A,B,C,D to be chosen independently. Thanks ! 
November 27th, 2016, 02:18 AM  #4  
Banned Camp Joined: Nov 2016 From: St. Louis, Missouri Posts: 28 Thanks: 4 Math Focus: arithmetic, fractions  Quote:
 