x²-4xy-1+4y²= 7.77²+4.46×7.77+2.23²= There must be a process. Let's go, brothers

x²-4xy-1+4y²
=x²-4xy+4y²-1
=（X-2Y）²-1
=（X-2Y+1)(X-2Y-1)
7.77²+4.46×7.77+2.23²
=7.77²+2×2.23×7.77+2.23²
=（7.77+2.23）²
=10²
=100

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