document.write( "Question 170002: Solve by substitution or elimination method:
\n" ); document.write( " 3x - 2y = 8
\n" ); document.write( " -12x + 8y = 32
\n" ); document.write( " Solve by substitution or elimination method:
\n" ); document.write( " 7x - 5y = 14
\n" ); document.write( " -4x + y = 27
\n" ); document.write( " Solve by substitution or elimination method:
\n" ); document.write( " -4x + 3y = 5
\n" ); document.write( " 12x - 9y = -15
\n" ); document.write( "
\n" ); document.write( "

Algebra.Com's Answer #125471 by Electrified_Levi(103)\"\" \"About 
You can put this solution on YOUR website!
Hi, Hope I can help,
\n" ); document.write( ".
\n" ); document.write( "Solve by substitution or elimination method:
\n" ); document.write( ".
\n" ); document.write( "3x - 2y = 8
\n" ); document.write( "-12x + 8y = 32
\n" ); document.write( ".
\n" ); document.write( "Solve by substitution or elimination method:
\n" ); document.write( ".
\n" ); document.write( "7x - 5y = 14
\n" ); document.write( "-4x + y = 27
\n" ); document.write( ".
\n" ); document.write( "Solve by substitution or elimination method:
\n" ); document.write( ".
\n" ); document.write( "-4x + 3y = 5
\n" ); document.write( "12x - 9y = -15
\n" ); document.write( ".
\n" ); document.write( "First we will solve the first system with substitution
\n" ); document.write( ".
\n" ); document.write( "3x - 2y = 8
\n" ); document.write( "-12x + 8y = 32
\n" ); document.write( ".
\n" ); document.write( "First we need to solve for a variable in one of the two equations, doesn't matter which letter, or equation, we will solve for \"y\" in the first equation
\n" ); document.write( ".
\n" ); document.write( "\"+3x+-+2y+=+8+\", we will move (-2y) to the right side
\n" ); document.write( ".
\n" ); document.write( "\"+3x+-+2y+=+8+\" = \"+3x+-+2y+%2B+2y+=+8+%2B+2y+\" = \"+3x+=+8+%2B+2y+\", now we need to move \"8\" to the left side
\n" ); document.write( ".
\n" ); document.write( "\"+3x+=+8+%2B+2y+\" = \"+3x+-+8+=+8+-+8+%2B+2y+\" = \"+3x+-+8+=+2y+\", to find \"y\" we need to divide each side by \"2\"
\n" ); document.write( ".
\n" ); document.write( "\"+3x+-+8+=+2y+\" = \"+%283x+-+8%29%2F2+=+2y%2F2+\" = \"+%283x+-+8%29%2F2+=+y+\"
\n" ); document.write( ".
\n" ); document.write( "\"+y+=+%283x+-+8%29%2F2+\", since \"y\" is equal to \"+%283x+-+8%29%2F2+\", we can replace \"y\" in the other equation with \"+%283x+-+8%29%2F2+\", then just solve for \"x\"
\n" ); document.write( ".
\n" ); document.write( "\"+-12x+%2B+8y+=+32+\" = \"+-12x+%2B+8%28%283x+-+8%29%2F2%29+=+32+\", now just solve for \"x\"
\n" ); document.write( ".
\n" ); document.write( "\"+-12x+%2B+8%28%283x+-+8%29%2F2%29+=+32+\" = \"+-12x+%2B+4%28%283x+-+8%29%2F1%29+=+32+\" = \"+-12x+%2B+4%283x+-+8%29+=+32+\", now we will use the distribution method
\n" ); document.write( ".
\n" ); document.write( "\"+-12x+%2B+highlight%284%29%28highlight%283x%29+-+8%29+=+32+\" = \"+-12x+%2B+highlight%284%29%283x+-+highlight%288%29%29+=+32+\"
\n" ); document.write( ".
\n" ); document.write( "Remember the + and - signs, \"+-12x+%2B+12x+-+32+=+32+\", adding the \"x\"'s
\n" ); document.write( ".
\n" ); document.write( "\"+-12x+%2B+12x+-+32+=+32+\" = \"+0x+-+32+=+32+\" = \"+-+32+=+32+\" ( False )
\n" ); document.write( ".
\n" ); document.write( "This means ( when the x's or y's cancel out, and there is a false statement) that there are no solutions, these lines are parallel, there is no intersection, and therefore no solutions
\n" ); document.write( ".
\n" ); document.write( "Here is the graph of this system
\n" ); document.write( ".
\n" ); document.write( "\"+graph+%28+300%2C300%2C-10%2C10%2C-10%2C10%2C+%283x+-+8%29%2F2%2C+%283x%2B8%29%2F2+%29+\"
\n" ); document.write( ".
\n" ); document.write( "Now we will solve the second system, by elimination
\n" ); document.write( ".
\n" ); document.write( "7x - 5y = 14
\n" ); document.write( "-4x + y = 27
\n" ); document.write( ".
\n" ); document.write( "Elimination is when you add the two equations together, and it gets rid of a variable, first we need to make sure the x's or y's in each equation are the same, or the negative of the other
\n" ); document.write( ".
\n" ); document.write( "We can eliminate any variable ( either x or y )
\n" ); document.write( ".
\n" ); document.write( "We will get rid of the y's
\n" ); document.write( ".
\n" ); document.write( "We need to either get both y's to \"5y\" or \"-5y\" or we need to get them to \"y\" or \"-y\", we will change the second equation to \"5y\"
\n" ); document.write( ".
\n" ); document.write( "\"+-4x+%2B+y+=+27+\", to get \"y\" to change to \"5y\" we need to multiply each side by (5)
\n" ); document.write( ".
\n" ); document.write( "\"+-4x+%2B+y+=+27+\" = \"+5%28-4x+%2B+y%29+=+5%2827%29+\" = \"+5%28-4x+%2B+y%29+=+135+\"
\n" ); document.write( ".
\n" ); document.write( "We will need to use the distribution method
\n" ); document.write( ".
\n" ); document.write( "\"+5%28-4x+%2B+y%29+=+135+\" = \"+highlight%285%29%28highlight%28-4x%29+%2B+y%29+=+135+\" = \"+highlight%285%29%28-4x+%2B+highlight%28y%29%29+=+135+\"
\n" ); document.write( ".
\n" ); document.write( "Remember the signs, \"+-20x+%2B+5y+=+135+\", this is our new equation
\n" ); document.write( ".
\n" ); document.write( "Now we will bring the firt equation to our second new equation
\n" ); document.write( ".
\n" ); document.write( "\"+7x+-+5y+=+14+\"
\n" ); document.write( ".
\n" ); document.write( "\"+-20x+%2B+5y+=+135+\"
\n" ); document.write( ".
\n" ); document.write( "We will now add the equations
\n" ); document.write( ".
\n" ); document.write( "\"+7x+-+5y+=+14+\"
\n" ); document.write( ".
\n" ); document.write( "\"+-20x+%2B+5y+=+135+\"
\n" ); document.write( ".
\n" ); document.write( "\"+7x+%2B+%28-20x%29+\" = \"+-13x+\"
\n" ); document.write( ".
\n" ); document.write( "\"+-5y+%2B+5y+\" = \"+0y+\" = \"+0+\"
\n" ); document.write( ".
\n" ); document.write( "\"+14+%2B+135+\" = \"149\"
\n" ); document.write( ".
\n" ); document.write( "It will become \"+-13x+%2B+0+=+149+\" = \"+-13x+=+149+\", to find \"x\" we need to divide each side by \"+-13+\"
\n" ); document.write( ".
\n" ); document.write( "\"+-13x+=+149+\" = \"+-13x%2F-13+=+149%2F-13+\" = \"+x+=+149%2F-13+\" = \"+x+=+-149%2F13+\", we can now replace \"x\" with \"++-149%2F13+\", in one of the two original equations
\n" ); document.write( ".
\n" ); document.write( "7x - 5y = 14
\n" ); document.write( "-4x + y = 27
\n" ); document.write( ".
\n" ); document.write( "We will use the second equation
\n" ); document.write( ".
\n" ); document.write( "\"+-4x+%2B+y+=+27+\" = \"+-4%28-149%2F13%29+%2B+y+=+27+\" = \"+%28-4%2F1%29%28-149%2F13%29+%2B+y+=+27+\" = \"+%28596%2F13%29+%2B+y+=+27+\"
\n" ); document.write( ".
\n" ); document.write( "Now we need to move \"+596%2F13+\" to the right side ( we will convert \"27\" into \"13ths\"
\n" ); document.write( ".
\n" ); document.write( "\"+596%2F13+%2B+y+=+27+\" = \"+596%2F13+%2B+y+=+351%2F13+\" = \"+%28596%2F13%29+-+%28596%2F13%29+%2B+y+=+%28351%2F13%29-%28596%2F13%29+\" = \"+y+=+%28351%2F13%29-%28596%2F13%29+\" = \"+y+=+-245%2F13+\"
\n" ); document.write( ".
\n" ); document.write( "\"+y+=+-245%2F13+\", we can check our answers by replacing \"x\" and \"y\" in both original equations
\n" ); document.write( ".
\n" ); document.write( "\"+x+=+-149%2F13+\"
\n" ); document.write( ".
\n" ); document.write( "\"+y+=+-245%2F13+\"
\n" ); document.write( ".
\n" ); document.write( "First equation, \"+7x+-+5y+=+14+\" = \"+7%28-149%2F13%29+-+5%28-245%2F13%29+=+14+\" = \"+%287%2F1%29%28-149%2F13%29+-+%28%285%2F1%29%28-245%2F13%29%29+=+14+\" = \"+%28-1043%2F13%29+-+%28-1225%2F13%29+=+14+\" = \"+%28-1043%2F13%29+%2B+1225%2F13+=+14+\" = \"+182%2F13+=+14+\" = \"+14+=+14+\" ( True )
\n" ); document.write( ".
\n" ); document.write( "Second equation, \"+-4x+%2B+y+=+27+\" = \"+-4%28-149%2F13%29+%2B+%28-245%2F13%29+=+27+\" = \"+%28-4%2F1%29%28-149%2F13%29+-+%28245%2F13%29+=+27+\" = \"+%28596%2F13%29+-+%28245%2F13%29+=+27+\" = \"+351%2F13+=+27+\" = \"+27+=+27+\", ( True )
\n" ); document.write( ".
\n" ); document.write( "\"+x+=+-149%2F13+\"
\n" ); document.write( ".
\n" ); document.write( "\"+y+=+-245%2F13+\"
\n" ); document.write( ".
\n" ); document.write( "Solution sets are in the form (x,y), our solution set is ( \"+-149%2F13+\", \"+-245%2F13+\" )
\n" ); document.write( ".
\n" ); document.write( "The graph of the system is
\n" ); document.write( ".
\n" ); document.write( "
\n" ); document.write( ".
\n" ); document.write( "The intersection is your answer
\n" ); document.write( ".
\n" ); document.write( "Now we can do the last system
\n" ); document.write( ".
\n" ); document.write( "-4x + 3y = 5
\n" ); document.write( "12x - 9y = -15
\n" ); document.write( ".
\n" ); document.write( "We will use the elimination method of solving this problem
\n" ); document.write( ".
\n" ); document.write( "Remember elimination is where you get rid of a variable
\n" ); document.write( ".
\n" ); document.write( "We will multiply the first equation by \"3\" to get rid of the \"y\"
\n" ); document.write( ".
\n" ); document.write( "\"+-4x+%2B+3y+=+5+\" = \"+3%28-4x+%2B+3y%29+=+3%285%29+\" = \"+3%28-4x+%2B+3y%29+=+15+\" we will use distribution
\n" ); document.write( ".
\n" ); document.write( "\"+3%28-4x+%2B+3y%29+=+15+\" = \"+highlight+%283%29%28highlight%28-4x%29+%2B+3y%29+=+15+\" = \"+highlight+%283%29%28-4x+%2B+highlight%283y%29%29+=+15+\"
\n" ); document.write( ".
\n" ); document.write( "Remember signs, \"+-12x+%2B+9y+=+15+\", now we can add the new first equation to the second equation
\n" ); document.write( ".
\n" ); document.write( "\"+-12x+%2B+9y+=+15+\"
\n" ); document.write( ".
\n" ); document.write( "\"+12x+-+9y+=+-15+\"
\n" ); document.write( ".
\n" ); document.write( "\"+-12x+%2B+12x+\" = \"+0x+\" = \"+0+\"
\n" ); document.write( ".
\n" ); document.write( "\"+9y+%2B+%28-9y%29+\" = \"+9y+-+9y+\" = \"+0y+\" = \"+0+\"
\n" ); document.write( ".
\n" ); document.write( "\"+15+%2B+%28-15%29+\" = \"+15+-+15+\" = \"+0+\"
\n" ); document.write( ".
\n" ); document.write( "It will become \"+0+%2B+0+=+0+\" = \"+0+=+0+\" (True)
\n" ); document.write( ".
\n" ); document.write( "This means ( when both x and y cancel out, and there is a true statement) that this is the same line, both equation will be one line, there is an infinite number of solutions ( since the equations are equal to one line )( or the second line is put on the first line )
\n" ); document.write( ".
\n" ); document.write( "Here is the graph of this system
\n" ); document.write( ".
\n" ); document.write( "\"+graph+%28+300%2C300%2C+-10%2C10%2C-10%2C10%2C+%284x+%2B+5%29%2F3%2C+%284x%2B5%29%2F3+%29+\"
\n" ); document.write( ".
\n" ); document.write( "Your answers are
\n" ); document.write( ".
\n" ); document.write( "First system of equations = \" no solutions \" ( since they are parallel lines )
\n" ); document.write( ".
\n" ); document.write( "Second system of equations = ( \"+-149%2F13+\", \"+-245%2F13+\" ) ( the lines intersect at point ( \"+-149%2F13+\", \"+-245%2F13+\" )
\n" ); document.write( ".
\n" ); document.write( "Third system of equations = \" infinite solutions \" ( since the two equations are the same line )
\n" ); document.write( ".
\n" ); document.write( "Hope I helped, Levi\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );