calculeaza mai simplu: va rooog

b) 7²-(4√3)²=49-16·3=49-48=√1=1
c) (1²-2·1·√7+√7²)- (1²+2·1·√7+√7²)=(1-2√7+7)-(1+2√7+7)=8-2√7-8-2√7=-4√7