Дам 50 баллов, помогите

А)
$\frac{9x^2-81}{3x+9}= \frac{(3x)^2-9^2}{3x+9}= \frac{(3x+9)(3x-9)}{3x+9}=3x-9=3*(-3)-9=-18$ ;
б)
$-\frac{(3a-9)}{(a^2-9)} =-\frac{3(a-3)}{(a-3)(a+3)} = \frac{3}{a+3} =\frac{3}{9+3}= \frac{3}{12} =0,25$ ;
в)
$\frac{4a(a^2-1)}{4a^2-4a} = \frac{4a(a-1)(a+1)}{4a(a-1)}=a+1=-1+1=0;$
г)
$\frac{a(x+1)-b(x+1)}{(a-b)*4} = \frac{(a-b)(x+1)}{4(a-b)}= \frac{x+1}{4} = \frac{3+1}{4} =1$ ;
д)
$5b+ \frac{8a-5b^2}{b} = \frac{5b^2+8a-5b^2}{b} = \frac{8a}{b} =\frac{8*8}{40} =1,6$