document.write( "Question 290651: Solve by substitution: 5x-4y= -7 x-3y/5= -2 \n" ); document.write( "
Algebra.Com's Answer #210322 by blwinbbbles(106)\"\" \"About 
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OK our two equations are:\r
\n" ); document.write( "\n" ); document.write( "1) 5x - 4y = -7 and
\n" ); document.write( "2) x - 3y/5 = -2\r
\n" ); document.write( "\n" ); document.write( "In substitution you need one of the equations to equal a single variable..in this case equation 2 is easiest to do that\r
\n" ); document.write( "\n" ); document.write( "So: x - 3y/5 = -2 add 3y/5 to both sides\r
\n" ); document.write( "\n" ); document.write( "x = 3y/5 - 2 Now you know what x equals and you can substitute it into equation 1\r
\n" ); document.write( "\n" ); document.write( "Hence:\r
\n" ); document.write( "\n" ); document.write( "5(3y/5 - 2) - 4y = -7 now solve it...
\n" ); document.write( "15y/5 - 10 - 4y = -7
\n" ); document.write( "3y - 10 - 4y = -7 add 10 to both sides
\n" ); document.write( "3y - 4y = 3 subtract the y's
\n" ); document.write( "- y = 3 and multiple both sides by -1...you cannot have a negative y
\n" ); document.write( "y = -3\r
\n" ); document.write( "\n" ); document.write( "Now use y = -3 in your original equation and solve for x\r
\n" ); document.write( "\n" ); document.write( "Use equation 1\r
\n" ); document.write( "\n" ); document.write( "5x - 4(-3) = -7
\n" ); document.write( "5x + 12 = -7 subtract 12 from both sides
\n" ); document.write( "5x = -19 divide by 5
\n" ); document.write( "x = -19/5 \r
\n" ); document.write( "\n" ); document.write( "so (-19/5, -3) are your cordinates..to check plug in numbers to both equation 1 and 2 then solve...this cordinate should work in both.\r
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