To eliminate the y terms and solve for x in the fewest steps, by which constants should the equations be multiplied by before adding the equations together?

First equation: 4x − 3y = 34

Second equation: 3x + 2y = 17

The first equation should be multiplied by 2 and the second equation by 3.
The first equation should be multiplied by 2 and the second equation by −3.
The first equation should be multiplied by 3 and the second equation by 4.
The first equation should be multiplied by 3 and the second equation by −4.

1 answer

To eliminate the \( y \) terms from the two equations, we want to make the coefficients of \( y \) in both equations equal in magnitude but opposite in sign, so that when we add them together, the \( y \) terms will cancel out.

The original equations are:

  1. \( 4x - 3y = 34 \)
  2. \( 3x + 2y = 17 \)

The coefficients of \( y \) are \(-3\) in the first equation and \(2\) in the second equation. We can make these coefficients equal by multiplying the first equation by \( 2 \) (to make the coefficient of \( y \) equal to \( -6 \)) and the second equation by \( 3 \) (to make the coefficient of \( y \) equal to \( 6 \)).

Here are the equations after multiplying:

  • First equation: \( 2(4x - 3y) = 2(34) \) → \( 8x - 6y = 68 \)
  • Second equation: \( 3(3x + 2y) = 3(17) \) → \( 9x + 6y = 51 \)

Now, if we sum these two adjusted equations:

\[ (8x - 6y) + (9x + 6y) = 68 + 51 \]

The \( -6y \) and \( +6y \) will cancel out, leaving us with:

\[ 17x = 119 \]

Now, we can solve for \( x \).

Thus, the correct choice for multiplying the equations is:

The first equation should be multiplied by 2 and the second equation by 3.