4
algebra

Which value of kk makes the system have no solution? {y=2x+7y=kx+3\begin{cases} y = -2x + 7 \\ y = kx + 3 \end{cases}

A

k=7k = 7

B

k=2k = -2

C

k=3k = 3

D

k=2k = 2

Correct Answer: B

Choice B is the correct answer. For no solution, we need parallel lines.

Analysis:

  • First line: slope = -2, y-intercept = 7
  • Second line: slope = kk, y-intercept = 3

Condition for parallel lines:

  • Same slope: k=2k = -2
  • Different y-intercepts: 7 ≠ 3 ✓ (already different)

With k=2k = -2, both lines have slope 2-2 but different y-intercepts, making them parallel with no intersection.

💡 Strategic Tip: For no solution in slope-intercept form, match the slopes but keep different intercepts.

Choice A is incorrect because k=7k = 7 gives different slopes (-2 and 7), resulting in one solution.

Choice C is incorrect because k=3k = 3 gives different slopes, resulting in one solution.

Choice D is incorrect because k=2k = 2 gives different slopes, resulting in one solution.