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2x+5y=102x+5y=10 and 3y+4x=123y+4x=12. find xx and yy

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Q. 2x+5y=102x+5y=10 and 3y+4x=123y+4x=12. find xx and yy
  1. Write Equations: Write down the system of equations.\newlineWe have the following system of equations:\newline11) 2x+5y=102x + 5y = 10\newline22) 4x+3y=124x + 3y = 12
  2. Eliminate y: Multiply the first equation by 22 and the second equation by 5-5 to eliminate yy.\newlineMultiplying the first equation by 22:\newline(2x+5y)×2=10×2(2x + 5y) \times 2 = 10 \times 2\newline4x+10y=204x + 10y = 20\newlineMultiplying the second equation by 5-5:\newline(4x+3y)×5=12×5(4x + 3y) \times -5 = 12 \times -5\newline20x15y=60-20x - 15y = -60
  3. Add Equations: Add the new equations together to eliminate yy.\newlineAdding the equations 4x+10y=204x + 10y = 20 and 20x15y=60-20x - 15y = -60:\newline(4x+10y)+(20x15y)=20+(60)(4x + 10y) + (-20x - 15y) = 20 + (-60)\newline4x20x+10y15y=20604x - 20x + 10y - 15y = 20 - 60\newline16x5y=40-16x - 5y = -40
  4. Correct Mistake: Since we made a mistake in the previous step by adding yy terms instead of canceling them out, we need to correct this.\newlineLet's add the equations again, but this time we will focus on canceling the yy terms:\newline(4x+10y)+(20x15y)=20+(60)(4x + 10y) + (-20x - 15y) = 20 + (-60)\newline4x20x+10y15y=20604x - 20x + 10y - 15y = 20 - 60\newline16x5y=40-16x - 5y = -40\newlineThis is incorrect because we should have:\newline4x20x=16x4x - 20x = -16x\newline10y15y=5y10y - 15y = -5y\newlineSo the correct equation after adding should be:\newline16x5y=40-16x - 5y = -40\newlineHowever, this does not help us eliminate yy. We need to go back and correctly eliminate yy by adding the right multiples of the original equations.

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