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my daughter needs help with two step equations using the addition method. Can someone help her with this problem:
\n" ); document.write( ":
\n" ); document.write( "The addition method means that when you add the equations one of the unknowns
\n" ); document.write( "is eliminated, often you have to mult one or both equations to get this to
\n" ); document.write( "happen, however, in these, you will eliminate y if just add them like they are:
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\n" ); document.write( "4x - y = 1
\n" ); document.write( "3x + y = 13
\n" ); document.write( "-------------- add
\n" ); document.write( "7x + 0 = 14; note that a +y and -y, added, is 0
\n" ); document.write( ":
\n" ); document.write( "So you have:
\n" ); document.write( "7x = 14
\n" ); document.write( ":
\n" ); document.write( "Divide both sides by 7 and you have:
\n" ); document.write( "1x = 14/7
\n" ); document.write( "x = 2
\n" ); document.write( ":
\n" ); document.write( "We know x, so we can find y by substituting 2 for x in the 1st equation:
\n" ); document.write( "4x - y = 1
\n" ); document.write( "4(2) - y = 1
\n" ); document.write( "8 - y = 1
\n" ); document.write( ":
\n" ); document.write( "Subtract 8 from both sides:
\n" ); document.write( "8 - 8 - y = 1 - 8
\n" ); document.write( "-y = -7
\n" ); document.write( ":
\n" ); document.write( "we have to have y positive, we get this by multiplying the equation by -1
\n" ); document.write( "y = + 7
\n" ); document.write( ":
\n" ); document.write( "Our solution is x = 2; y = 7
\n" ); document.write( ":
\n" ); document.write( "Check this by substituting for x & y in the 2nd equation:
\n" ); document.write( "3x + y = 13
\n" ); document.write( "3(2) + 7 = 13
\n" ); document.write( "6 + 7 = 13; proves our solutions are correct
\n" ); document.write( ":\r
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