Надо а+4/а^2-10а+25 - а+2/а^2-25 при а = 7,5

(a+4)/(a-5)²-(a+2)/(a-5)(a+5)=(a²+5a+4a+20-a²+5a-2a+10)/(a-5)²(a+5)=
=(12a+30)/(a-5)²(a+5)=6(2a+5)/(a-5)²(a+5)
a=7,5
6(15+5)/(2,5*12,5=6*20/(2,5*12,5)=120/31,25=3,84