докажите тождество:
5-(5-(5-(5-x)))=x

x-(x-(x-(x-5)))=5

5-(5-(5-5+х)=5-(5-5+5-х)=5-5+5-5+х= х

Х-(х-(х-х+5)=х-(х-х+х-5)=х-х+х-х+5=5

Читд