A
1)a-1/(1-a)=a+1/(a-1)=(a²-a+1)/(a-1)
2)(a²-a+1)/(a-1)*(a-1)²/(a²-a+1)=a-1=6-1=5
б
1)1/a-1/(b+c)=(b+c-a)/[a(b+c)]
2)1/a+1/(b+c)=(b+c+a)/[a(b+c)]
3)(b+c-a)/[a(b+c)]*[a(b+c)]/(b+c+a)=(b+c-a)/(b+c+a)
4)1+(b²+c²-a²)/2bc=(2bc+b²+c²-a²)/2bc=[(b+c)²-a]/2bc=
=(b+c-a)(b+c+a)/2bc
5)(b+c-a)/(b+c+a) * (b+c-a)(b+c+a)/2bc=(b+c-a)²/2bc
6)(b+c-a)²/2bc * (a-b-c)/abc=-(b+c-a)²/2bc *abc/(b+c-a)=-(a-b-c)a/2=
=(0,02+11,05-1,07)*0,02/2=10*0,01=0,1