( 5A + 3B) /( 4A + 5B ) = ?
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6A + 7B = 0
6A = - 7B
A = ( - 7/6B )
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( 5 * ( - 7/6B ) + 3B ) / ( 4 * ( - 7/6B ) + 5B ) = ( - 35/6B + 3B ) / ( - 28/6B + 5B ) =
= ( - 35/6B + 18/6B ) / ( - 28/6B + 30/6B ) = ( - 17/6B ) / ( 2/6B ) = ( - 17/2 ) =
= ( - 8,5 )
Ответ ( - 8,5 )