by 
yvette
ANSWERS: 4
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-6x+3y=21y+2x -6x=18y+2x -8x=18y I think that's right.....Been a long time. Okay now that I see the rest of the problem unlike before...... -8x=18y+7
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-6x+3y=21y -3[2x-y]=21y 2x-y=21y/-3 2x-y=-7y 2x=-7y+y 2x=-6y x=-6y/2 x=-3y---------1 from 1 we assume y=-x/3 21y=7+2x 21[-x/3]=7+2x -7x=7+2x -7x-2x=7 -9x=7 x=7/-9 y=[7/-9]/3] y=7/-27] y=-7/27
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I assume you have two equations: -6x + 3y = 21 y = 7 + 2x Swap the second equation round: -6x + 3y = 21 2x + 7 = y Add three of the second equation to the first: 21 + 3y = 21 + 3y Hang on a minute - something fishy here! The two equations are equavalent to each other: y = 7 + 2x so 3y = 21 + 6x so - 6x + 3y = 21 Therefore you can't solve the equation any more than it is now. y = 7 + 2x OR x = (y - 7)/2
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x = 0, y = 7 -6x + 3y = 21 -6*0 + 3*7 = 21 0 + 21 = 21 21 = 21 therefore, it is proven that 0 is a valid value for x y = 7 + 2x 7 = 7 + 2*0 7 = 7 + 0 7 = 7 therefore, it is proven that 7 is a valid value for y
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