9

Set 8: Linear Functions (Advanced)

Explanation

Answer: A

Two lines have slopes m1=am_1 = a and m2=1/am_2 = 1/a. Are they perpendicular?

A.

No, unless a=1a = -1 or a=1a = 1 (with sign change)

✓ Correct
B.

Yes, always

C.

No, never

D.

Only if a=0a = 0

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Check product rule. 1. Product: a×(1/a)=1a \times (1/a) = 1. 2. Condition: Perpendicular lines must have a product of 1-1. 3. Conclusion: They are reciprocals, but not negative reciprocals. So generally No. Strategic Tip: Don't forget the negative sign! mm and 1/m-1/m are perpendicular. Choice B is incorrect because product is 1. Choice C is incorrect because they could be if aa involves complex numbers (out of scope) or specific sign errors in setup. Choice D is incorrect because undefined.

Key Steps:

The correct answer is No, unless a=1a = -1 or a=1a = 1 (with sign change)

Why others are wrong:
B: Choice B 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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