Geometryhard · Past Paper
If (a, 0), (0, b), and (1, 1) are collinear, then 1/a + 1/b = ?
A0
B1
C2
D-1
✓ Correct Answer: B — 1
Slope 1 = (b-0)/(0-a) = -b/a. Slope 2 = (1-b)/(1-0) = 1-b. -b/a = 1-b => -b = a - ab => ab = a + b => 1 = 1/b + 1/a.
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