[ ( x + 4 )( x + 5 ) + 4( x + 1 )( x + 5) - 5( x + 1 )( x + 4 ) ] / [( x + 1 )( x + 4)( x + 5 )] = ( x^2 + 9x + 20 + 4x^2 + 24x +20 - 5x^2 - 25x - 20) / [( x + 1 )( x + 4)( x + 5 )] =
( - 2x + 20 ) / [( x + 1 )( x + 4)( x + 5 )] = ( - 2)( x - 10) / [( x + 1 )( x + 4)( x + 5 )]
