#color(blue)("Using Gauss Jordon elimination")#
#" "color(white)(.)xcolor(white)(.)ycolor(white)(.)"answer"#
#" "[[1,3,"|",11],[1,4,"|",14]]#
#" "Row2-Row1#
#" "darr#
#" "[[1,3,"|",11],[0,1,"|",3]]#
#" "Row1-3(Row2)#
#" "darr#
#" "[[1,0,"|",2],[0,1,"|",3]]" "larr [[x],[y]]#
#color(white)(.)#
#=>[[1,0],[0,1]] color(white)(.)[[x],[y]] = [[2],[3]]#
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("Using Linear Algebra")#
#A=[[1,3],[1,4]]#
#color(white)(.)#
#X=[[x],[y]]#
#B=[[11],[14]]#
#=>AX=B#
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(brown)("Consider the Algebra method of determining "x)#
Given:#" "3x=4#
Divide both side by 3 #-> 1/3xx3x=1/3xx4#
We multiply the 3 by 3 inverse to turn the coefficient of #x# into 1
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(brown)("Using the Algebra method shown above")#
Multiply both sides by #A" inverse. written as "color(blue)(A^(-))#
#color(brown)(=>color(blue)(A^(-))AX" "=" "color(blue)(A^(-))B)#
#=>X=A^(-)B# ...................................Equation(1)
Checked in Maple:
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("Determine "A^(-))#
#color(brown)("Method 1")#
Write the original matrix as:
#" "[[1,3,"|",1,0],[1,4,"|",0,1]]#
And conduct a Gauss Jordon elimination on the LHS
#" "Row2-Row1#
#" "darr#
#" "[[1,3,"|",1,0],[0,1,"|",-1,1]]#
#" "Row1-3(Row2)#
#" "darr#
#" "[[1,0,"|",4,-3],[0,1,"|",-1,1]] => A^(-)=[[4,-3],[-1,1]]#
,.....................................................................................
#color(brown)("Method 2 - Shortcut approach")#
Multiply a modified version of #[[1,3],[1,4]]# by its inverted determinant.
For #[[a,b],[c,d]]# the determinant is #ab-cd#
and the modified matrix is #[[d,-b],[-c,a]]#
#D=(1xx4)-(1xx3)=1#
Thus #A^(-)= 1xx[[4,-3],[-1,1]]#
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("Finish the calculation for Equation(1)")#
#=>X=A^(-)B# ...................................Equation(1)
#[[4,-3],[-1,1]] [[11],[14]] = [[2],[3]]#