A=[8 1 -1; 1 2 9; 1 -7 2];>> B= [8; 12; -4;];>> X=INV(A)*B??? Capitalized internal function INV; Caps Lock may be on.

>> X=inv (A)*B

X =

1.0000 1.0000 1.0000

>> AX1=[8 1 -1;1 2 2 9; -4 -7 2];??? Error using ==> vertcatAll rows in the bracketed expression must have the same number of columns.

>> AX1=[8 1 -1; 12 2 9; -4 -7 2];>> AX2=[8 8 -1; 1 12 9; 1 -4 2];>> AX3=[8 1 8; 1 2 12; 1 -7 -4];>> X1=det(AX1)/det(A)

X1 =

1

>> X2=det(AX2)/det(A)

X2 =

1

>> X3=det(AX3)/det(A)

X3 =

1

>> syms L11 L21 L22 L31 L32 L33 U12 U13 U23>> L=[L11 0 0; L21 L22 0; L31 L32 L33];>> U=[1 U12 U13; 0 1 U23; 0 0 1];>> D=L*U D = [ L11, L11*U12, L11*U13][ L21, L21*U12+L22, L21*U13+L22*U23][ L31, L31*U12+L32, L31*U13+L32*U23+L33]

>> L1=[8 0 0; 1 1.875 0; 1 -7.125 36.7525];>> NilaiX=inv(L1*U1)*B??? Undefined function or variable 'U1'.

>> U1=[1 0.125 -0.125; 0 1 4.86; 0 0 1];>> NilaiX=inv(L1*U1)*B

NilaiX =

1.0001 1.0004 1.0013

>>