3
algebra

For what value of kk does the system have no solution? {3x2y=76x4y=k\begin{cases} 3x - 2y = 7 \\ 6x - 4y = k \end{cases}

A

k=7k = 7

B

k=10k = 10

C

k=14k = 14

D

Any value except 14

Correct Answer: D

Choice D is the correct answer. For no solution, the system must represent parallel lines (same coefficients on xx and yy, but different constants).

Step 1: Notice that the second equation has coefficients that are exactly double the first:

  • First equation: 3x2y=73x - 2y = 7
  • Second equation: 6x4y=k6x - 4y = k

Step 2: If we multiply the first equation by 2: 2(3x2y)=2(7)2(3x - 2y) = 2(7)6x4y=146x - 4y = 14

Step 3: For the lines to be parallel but not identical:

  • If k=14k = 14: the lines are identical → infinitely many solutions
  • If k eq14k \ eq 14: the lines are parallel → no solution

💡 Strategic Tip: Parallel lines occur when left sides are proportional but right sides are not.

Choice A is incorrect becausek=7k = 7 gives no solution (not 14), but it's not the only value.

Choice B is incorrect becausek=10k = 10 gives no solution, but it's not the only value.

Choice C is incorrect becausek=14k = 14 gives infinitely many solutions, not no solution.