49/7b-b^2-7/b если b=-3

49/7b - ( b^2 - 7 )/b = ( 49 - 7( b^2 - 7 ) / 7b = ( 49 - 7b^2 + 49 ) / 7b = ( 7( 14 - b^2 )) / 7b = ( 14 - b^2 ) / b
b = - 3
( 14 - ( - 3 )^2 ) / ( - 3 ) = ( 14 - 9 ) / ( - 3 ) = - 5/3 = - 1 2/3

[tex] \frac{49}{7b} - b^{2} - \frac{7}{b} = \frac{7}{b} - b^{2} - \frac{7}{b} =- b^{2} [/tex]
b=-3
[tex] -(-3)^{2} =-9[/tex]
Ответ: -9