Straight Line Question 244
Question: If the straight lines $ ax+may+1=0, $ $ bx+(m+1)by+1=0 $ and $ cx+(m+2)cy+1=0 $ are concurrent, then a, b, c form $ (m\ne 0) $
Options:
A) An A.P. only for m=1
B) An A.P. for all m
C) A G.P. for all m
D) A H.P. for all m
Correct Answer: D $ \Rightarrow \frac{1}{c}-\frac{1}{b}-\frac{1}{b}+\frac{1}{a}=\frac{1}{c}+\frac{1}{a}-\frac{2}{b}=0 $ $ \therefore \frac{1}{a},\frac{1}{b},\frac{1}{c} $ are in A.P., for all m.
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Answer:
Solution:
$ \therefore $ a, b, c are in H.P., for all m.
BETA
