Multiple choice general knowledge math & puzzles

The line passing through the points (5, 1, a) and (3, b, 1) crosses the yz-plane at the point (0, 17/2, -13/2) Then

  1. a = 2, b = 8

  2. a = 4, b = 6

  3. a = 6, b = 4

  4. a = 8, b = 2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the line equation (x-5)/(0-5) = (y-1)/(17/2-1) = (z-a)/(-13/2-a). For x=3: (3-5)/-5 = 2/5. Then (b-1)/(15/2) = 2/5 => b-1=3 => b=4. And (1-a)/(-13/2-a) = 2/5 => 5-5a = -13-2a => 18=3a => a=6.

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