a)47²-37²=(47-37)(47+37)=10·84=840
б)53²-63²=(53-63)(53+63)=10·116=1160.
b)126²-74²=(126+74)(126-74)=200·52=10400.
г)21,3²-21,2²=(21,3-21,2)(21,3+21,2)=0,1·42,5=4,25,
д)0,849²-0,151²=(0,849+0,151)(0.849-0,151)=1·0,698=0,698,
е)=(5 2/3 -4 1/3)(5 2/3+4 1/3)=1/3·10=10/3.