Найдите значения дроби: x^2-8x-33 10x+30 при x=-9

1) х^2 - 8х - 33 = ( x - 10 )( x + 3 )
D = 64 + 132 = 196 = 14^2
X1 = ( 8 + 14 ) : 2 = 10
X2 = ( 8 - 14 ) : 2 = - 3
2) 10x + 30 = 10( x + 3 )
3) ( ( x - 10 )( x + 3 )) / ( 10( x + 3 )) = ( x - 10 ) / 10 = 0,1x - 1
4) x = - 9
0,1•( - 9 ) - 1 = - 0,9 - 1 = - 1,9