document.write( "Question 712792: what method can i use to solve 2x+3y=9. -3x+3y=-6 \n" ); document.write( "
Algebra.Com's Answer #438157 by Simnepi(216)\"\" \"About 
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since both equations have the same number of y's then the best method is elimination.
\n" ); document.write( "here's how
\n" ); document.write( "2x+3y=9 let's call this equation (1)
\n" ); document.write( "-3x+3y=-6 let's call this equation (2)
\n" ); document.write( "because they are the same sign, i.e. both positive, then we eliminate them by subtraction. if the signs were different we would eliminate them by adding.
\n" ); document.write( "(signs Same, Subtract : signs Different, aDd is how i tell my learners to remember this, emphasising the capital letters!)
\n" ); document.write( "now back to the problem
\n" ); document.write( "subtracting the equations left hand sides and right hand sides gives
\n" ); document.write( "2x+3y-(-3x+3y)=9-(-6)
\n" ); document.write( "removing the brackets gives us
\n" ); document.write( "2x+3y+3x-3y=9+6
\n" ); document.write( "(notice how the negative sign outside the bracket changes all the signs of the terms inside the bracket when it is removed)
\n" ); document.write( "simplifying gives
\n" ); document.write( "5x=15 so
\n" ); document.write( "x=3
\n" ); document.write( "now we use this value in one of the original equations i.e.
\n" ); document.write( "2x+3y=9
\n" ); document.write( "giving
\n" ); document.write( "2(3)+3y=9
\n" ); document.write( "i.e.
\n" ); document.write( "6+3y=9
\n" ); document.write( "therefore
\n" ); document.write( "3y=3 so
\n" ); document.write( "y=1
\n" ); document.write( " \n" ); document.write( "
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