Упростите выражение и найдите его значение:

№264
$1) \frac{x-4}{ x^{2} +12x+36} - \frac{x-1}{ x^{2} -36}$
$\frac{x-4}{(x+6)^2} -\frac{x-1}{(x+6)*(x-6)}=\frac{(x-4)*(x-6)-(x-1)*(x+6)}{(x+6)^2*(x-6)}=\frac{x^2-10x+24-x^2+5x+6}{(x+6)^2*(x-6)}$
$\frac{x^2-10x+24-x^2+5x+6}{(x+6)^2*(x-6)}=\frac{-5x+30}{(x+6)^2*(x-6)}=\frac{-5(x-6)}{(x+6)^2(x-6)}=\frac{-5}{(x+6)^2}$
$\frac{-5}{(x+6)^2}=\frac{-5}{(1,5+6)^2}=\frac{-5}{7.5^2} =\frac{-5}{56.25}=-\frac{1}{11.25}$

2) $\frac{a+4}{a^2-10a+25}-\frac{a+2}{a^2-25}=\frac{a+4}{(a-5)^2}-\frac{a+2}{(a+5)(a-5)}$
$\frac{a+4}{(a-5)^2}-\frac{a+2}{(a+5)(a-5)}=\frac{(a+4)*(a+5)-(a+2)*(a-5)}{(a-5)^2(a+5)}=\frac{a^2+9a+20-a^2-3a-10}{(a-5)^2(a+5)}$
$\frac{a^2+9a+20-a^2-3a+10}{(a-5)^2(a+5)}=\frac{6a+30}{(a-5)^2(a+5)}=\frac{6(a+5)}{(a-5)^2*(a+5)}=\frac{6}{(x-5)^2}$
$\frac{6}{(7.5-5)^2}=\frac{6}{2.5^2}=\frac{6}{6.25}=0.96$

Но я не уверен