( (a+6b)/(a^2-6ab) - 1/a ) : b/(6b-a) = ( (a+6b)/a(a-6b) - (a-6b)/a(a-6b) ) : b/(6b-a) = ( ( (a+6b)-(a-6b) )/a(a-6b) ) : b/(6b-a) = ( (a+6b-a+6b)/a(a-6b) ) : b/(6b-a) = ( 12b/a(a-6b) ) : b/(6b-a) = 12b*(6b-a)/a(a-6b)*b = -12/a
При a=9,6
-12/a = -12/9,6 = -1,25
Ответ: -1,25