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Set 13: Systems of Equations (Advanced)

Explanation

Answer: B

Which system represents parallel lines?

I. {y=2x+5y=2x3\begin{cases} y = 2x + 5 \\ y = 2x - 3 \end{cases}

II. {y=2x+5y=12x+5\begin{cases} y = 2x + 5 \\ y = -\frac{1}{2}x + 5 \end{cases}

III. {y=2x+52y=4x+10\begin{cases} y = 2x + 5 \\ 2y = 4x + 10 \end{cases}

A.

I and II only

B.

I only

✓ Correct
C.

II and III only

D.

I and III only

Detailed Explanation

Choice B is correct. Choice B is the correct answer. System I: y=2x+5y = 2 x + 5 and y=2x3y = 2 x - 3 - Same slope (2), different intercepts - Parallel lines ✓ System II: y=2x+5y = 2 x + 5 and y=12x+5y = -\frac{1}{2}x + 5 - Different slopes (2 and 12-\frac{1}{2}) - Strategic Tip: - Parallel: same slope, different intercepts - Perpendicular: slopes multiply to -1 - Identical: same slope, same intercept Choice A is incorrect because System II has perpendicular lines, not parallel. Choice C is incorrect because System III has identical lines, and System II is perpendicular. Choice D is incorrect because System III has identical lines, not parallel (though all identical lines are technically parallel, "parallel" usually means "distinct parallel lines").

Key Steps:

The correct answer is I only

Why others are wrong:
A: Choice A is incorrect and may result from a calculation error.
C: Choice C is incorrect and may result from a calculation error.
D: Choice D is incorrect and may result from a calculation error.

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