Đáp án:
\[B=3(2^2+1)(2^4+1)...(2^{64}+1)+1\] \[\to B=(2^2-1)(2^2+1)(2^4+1)...(2^{64}+1)+1\] \[\to B=(2^4-1)(2^4+1)...(2^{64}+1)+1\] \[\to B=(2^8-1)(2^8+1)(2^{16}+1)(2^{32}+1)(2^{64}+1)+1\] \[\to B=(2^{16}-1)(2^{16}+1)(2^{32}+1)(2^{64}+1)+1\] \[\to B=(2^{32}-1)(2^{32}+1)(2^{64}+1)+1\] \[\to B=(2^{64}-1)(2^{64}+1)+1\] \[\to B=(2^{128}-1)+1=2^{128}\]
\[C=(a+b+c)^2+(a+b-c)^2-2(a+b)^2\] \[\to C=(a+b+c)^2+(a+b-c)^2-(a+b)^2-(a+b)^2\]\[\to C=\bigg[(a+b+c)^2-(a+b)^2\bigg]+\bigg[(a+b-c)^2-(a+b)^2\bigg]\] \[\to C=(a+b+c-a-b)(a+b+c+a+b)+(a+b-c-a-b)(a+b-c+a+b)\] \[\to C=c(2a+2b+c)+(-c)(2a+2b-c)\] \[\to C=c(2a+2b+c) - c(2a+2b-c)\] \[\to C=c\big(2a+2b+c-2a-2b+c\big)\] \[\to C=2c^2\]
