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  1. If  
    3a + 4b
    =
    3a − 4b
    , then
    3c + 4d3c − 4d
    1. ab = cd
    2. ad = bc
    3. ac = bd
    4. a = b = c ≠ d
Correct Option: B

3a + 4b
=
3a − 4b
3c + 4d3c − 4d

⇒ 
3a + 4b
=
3c + 4d
3a − 4b3c − 4d

By componendo and dividendo,
3a + 4b + 3a − 4b
=
3c + 4d + 3c − 4d
3a + 4b − 3a + 4b3c + 4d − 3c + 4d

⇒ 
6a
=
6c
8b8d

⇒ 
a
=
c
bd

⇒  ad = bc



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