中等MATH-GEOM-002
Which line is perpendicular to y = 2x + 1?
A. y = 2x − 3
B. y = −2x + 1
C. y = (1/2)x + 4
D. y = (−1/2)x + 4✓ 答案
解說
Perpendicular slopes multiply to −1, so the slope must be −1/2. The slope 2 is parallel. The slope −2 is the negative of the original slope, not its negative reciprocal. The slope 1/2 has the right size but the wrong sign.