Question

O eliminate the y-terms and solve for x in the fewest steps, by which constants should the equations be multiplied? First Equation: 5x − 4y = 28 Second equation: 3x - 9y = 30
A.The first equation should be multiplied by 3 and the second equation by 5.B.The first equation should be multiplied by 3 and the second equation by −5.C.The first equation should be multiplied by 9 and the second equation by 4.D.The first equation should be multiplied by 9 and the second equation by −4.

Answer 1

"D.The first equation should be multiplied by 9 and the second equation by −4." makes sense.  Let's do this work:

First Equation: 5x − 4y = 28 Second equation: 3x - 9y = 30

45x - 36y = 252
-12x+36y = -120
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33 x = 132, so x = 4.  And so on.