document.write( "Question 55821: 2a-5b+c=5
\n" ); document.write( "3a+2b-c=17
\n" ); document.write( "4a+3b+2c=17
\n" ); document.write( "

Algebra.Com's Answer #37919 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
2a - 5b + c = 5
\n" ); document.write( "3a + 2b - c = 17
\n" ); document.write( "4a + 3b + 2c = 17
\n" ); document.write( ":
\n" ); document.write( "If we mult the 1st eq by -1 we can eliminate c from all three equation:
\n" ); document.write( "-2a + 5b - c = -5
\n" ); document.write( " 3a + 2b - c = 17
\n" ); document.write( " 4a + 3b + 2c = 17
\n" ); document.write( "---------------------add
\n" ); document.write( " 5a + 10b = 29
\n" ); document.write( ":
\n" ); document.write( "Adding the 1st and 2nd equations eliminates c also:
\n" ); document.write( "2a - 5b + c = 5
\n" ); document.write( "3a + 2b - c = 17
\n" ); document.write( "-------------------add
\n" ); document.write( "5a - 3b = 22
\n" ); document.write( ":
\n" ); document.write( "WE have two equations with two unknowns a & b
\n" ); document.write( "5a + 10b = 29
\n" ); document.write( "5a - 3b = 22
\n" ); document.write( "--------------- subtract
\n" ); document.write( " 13b = 7
\n" ); document.write( " b = 7/13
\n" ); document.write( ":
\n" ); document.write( "Find a using the equation 5a - 10b = 29, substitute 5/13 for b
\n" ); document.write( "5a + 10(7/13) = 29
\n" ); document.write( "5a + 70/13 = 29
\n" ); document.write( " 5a = 377/13 - 70/13, (converted 29 to 13th)
\n" ); document.write( " 5a = 307/13
\n" ); document.write( " a = (307/13) / 5
\n" ); document.write( " a = 307/65
\n" ); document.write( ":
\n" ); document.write( "Find c using the 1st equation, 2a - 5b + c = 5, substitute for a & b
\n" ); document.write( "2(307/65) - 5(7/13) + c = 5
\n" ); document.write( ":
\n" ); document.write( "614/65 - 5(35/65) + c = 5; convert 7/13 to 65th
\n" ); document.write( ":
\n" ); document.write( "614/65 - 175/65 + c = 5
\n" ); document.write( ":
\n" ); document.write( "439/65 + c = 5
\n" ); document.write( ":
\n" ); document.write( "c = 325/65 - 439/65; converted 5 to 65th
\n" ); document.write( ":
\n" ); document.write( "c = -114/65
\n" ); document.write( ":
\n" ); document.write( "So we end up with these nasty fractions (the guy who dreamed this up must be a sadist)
\n" ); document.write( "a = 307/65; b = 7/13; c = -114/65
\n" ); document.write( ":
\n" ); document.write( "Because of the tremendous opportunity for error here, I check these solutions using the matrix feature on the TI*83 and got the decimal equivalent for each one of these fractions. \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );