a/ \(127^2+146\cdot127+73^2=127^2+2\cdot73\cdot127+73^2=\left(127+73\right)^2=200^2=40000\)
b/ \(100^2-99^2+98^2-97^2+...+2^2-1^2=\left(100^2-99^2\right)+\left(98^2-97^2\right)+...+\left(2^2-1^2\right)\)
\(=100+99+98+97+...+2+1=\frac{\left(100\right)\left(100+1\right)}{2}=5050\)
c/ \(34^2+66^2+68\cdot66=34^2+66^2+2\cdot34\cdot66=\left(34+66\right)^2=100^2=10000\)