document.write( "Question 30328: AX+BY=P
\n" ); document.write( "BX-AY=Q SOLVE FORX&Y
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Algebra.Com's Answer #17003 by sdmmadam@yahoo.com(530)\"\" \"About 
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AX+BY=P ----(1)multiplied by A
\n" ); document.write( "BX-AY=Q ----(2)multiplied by B\r
\n" ); document.write( "\n" ); document.write( "(1) is multiplied by A and (2) is multiplied by B
\n" ); document.write( "so that the coefficients of Y are made the same.\r
\n" ); document.write( "\n" ); document.write( "A^2X +(AB)Y = AP ----(3)
\n" ); document.write( "B^2X -(AB)Y = BQ ----(4)
\n" ); document.write( "(3) + (4) gives
\n" ); document.write( "(A^2+B^2)X = AP+BQ
\n" ); document.write( "Dividing by (A^2+B^2)
\n" ); document.write( "X = (AP+BQ)/(A^2+B^2) ----(*)
\n" ); document.write( "Putting (*) in (1)
\n" ); document.write( "AX+BY =P
\n" ); document.write( "A times[(AP+BQ)/(A^2+B^2)]+BY = P
\n" ); document.write( "Multiplying by (A^2+B^2)
\n" ); document.write( "A(AP+BQ) +B(A^2+B^2)Y = P(A^2+B^2)
\n" ); document.write( "B(A^2+B^2)Y = P(A^2+B^2)-A(AP+BQ)
\n" ); document.write( "B(A^2+B^2)Y = PA^2+PB^2-PA^2-ABQ
\n" ); document.write( "B(A^2+B^2)Y = (PA^2-PA^2)+PB^2-ABQ
\n" ); document.write( "B(A^2+B^2)Y = (PA^2-PA^2)+PB^2-ABQ
\n" ); document.write( "B(A^2+B^2)Y = 0+B(BP-AQ)
\n" ); document.write( "B(A^2+B^2)Y = B(BP-AQ)
\n" ); document.write( "Dividing by B(A^2+B^2)
\n" ); document.write( "Y = (BP-AQ)/(A^2+B^2)
\n" ); document.write( "Answer: X = (AP+BQ)/(A^2+B^2) and Y = (BP-AQ)/(A^2+B^2)
\n" ); document.write( "Note:Instead of substituting for X and getting Y,we may give a similar treatment of equalising coefficients and using subtractilon to get rid of X to get Y.
\n" ); document.write( "Verification:Since (1) was used to find Y substituting for X we shall
\n" ); document.write( "use (2) for verification.
\n" ); document.write( "BX-AY=Q ----(2)
\n" ); document.write( "Putting X = (AP+BQ)/(A^2+B^2) and Y = (BP-AQ)/(A^2+B^2)in this
\n" ); document.write( "LHS = B(AP+BQ)/(A^2+B^2) - A(BP-AQ)/(A^2+B^2)
\n" ); document.write( "=[1/(A^2+B^2)]multiplied by[B(AP+BQ)- A(BP-AQ)]
\n" ); document.write( "=[1/(A^2+B^2)]multiplied by(ABP+B^2Q-ABP+A^2Q]
\n" ); document.write( "=(ABP-ABP+A^2Q+B^2Q]/(A^2+B^2)
\n" ); document.write( "=[0+(A^2+B^2)Q]/(A^2+B^2)
\n" ); document.write( "=(A^2+B^2)Q]/(A^2+B^2)
\n" ); document.write( "=Q (cancelling (A^2+B^2)
\n" ); document.write( "=RHS\r
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