9c^2-4d^2/18c^2d - 12cd^2, при c=2/3, y=-0.6
С решением.

1) 18с^2d - 12cd^2 = 6cd( 3c - 2d ) 2) 9c^2 - 4d^2 = ( 3c - 2d )( 3c + 2d ) 3) ( 6cd( 3c - 2d )) / ( ( 3c - 2d )( 3c + 2d )) = 6cd / ( 3c + 2d ) 4) c = 2/3 ; d = - 0,6 = - 3/5 ( 6•2/3•( - 3/5 )) / ( 3•2/3 + 2•( - 3/5 )) = ( - 12/5 ) / ( 2 - 6/5 ) = ( - 12/5 ) / ( 4/5 ) = - 12/4 = - 3 Ответ ( - 3 )