Question

prove it.... .........

Answer 1

Given :

a : b :: c : d

==> a / b = c / d

Multiplying both sides by 4 / 7 to get :

==> 4 a / 7 b = 4 c / 7 d

By componendo and dividendo :

==> ( 4 a + 7 b ) / ( 4 a - 7 b) = ( 4 c + 7 d ) / ( 4 c - 7 d )

By invertendo :

==> ( 4 a + 7 b ) / ( 4 c + 7 d ) = ( 4 a - 7 b ) / ( 4 c -  7 d )

[ P.R.O.V.E.D ]

Hope it helps !

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Answer 2

your answer is here