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Solve the system by addition.
\n" ); document.write( " 4x – 4y = 9 ----(1)
\n" ); document.write( " 8x + 2y = –7 ----(2) X2
\n" ); document.write( "(to equalise the coefficients of y (numerically) multiply (2) through out by 2
\n" ); document.write( " 16x+4y = -14 ----(3)
\n" ); document.write( " 4x – 4y = 9 ----(1)
\n" ); document.write( " (3) + (1) implies
\n" ); document.write( " (16x+4x) +(4y-4y)= (-14+9) (adding left with left and right with right)
\n" ); document.write( " 20x +0 = -5
\n" ); document.write( " 20x = -5
\n" ); document.write( " x = -5/20 = -1/4
\n" ); document.write( "Putting x=-1/4 in (1)
\n" ); document.write( "4x-4y = 9
\n" ); document.write( "4X(-1/4) - 4y = 9
\n" ); document.write( "-1-4y = 9
\n" ); document.write( "-1-9 =4y
\n" ); document.write( "-10 = 4y
\n" ); document.write( "y = (-10)/4 = -5/2
\n" ); document.write( "Answer: x =(-1/4) and y = (-5/2)
\n" ); document.write( "Verification: putting x =(-1/4) and y = (-5/2)in 8x + 2y = –7 ----(2)
\n" ); document.write( "LHS = 8x+2y = 8X(-1/4)+2X(-5/2) = -2-5 = -7 =RHS
\n" ); document.write( "Hence our values are right
\n" ); document.write( "Note:You may divide (1) through out by 2 and write it as 2x – 2y = 9/2----(*) and then add it(*) up with (2)which is 8x + 2y = –7 ----(2)giving
\n" ); document.write( "(2x+10x)= (9/2-7)
\n" ); document.write( "10x = -5/2 which givis x=-5/4 and therefore y = -5/2\r
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