38.9²-2×38.9×48.9+48.9²
=(38.9-48.9)²
=(-10)²
=100
24²+24×32+16²
=24²+2×24×16+16²
=(24+16)²
=40²
=1600
M=x²+y²,N=2xy
M-N=x²+y²-2xy=(x-y)²≥0
∴M≥N (当x=y时取等号
a²+2ab+b²=0
即(a+b)²=0
∴a+b=0
∴a(a+4b)-(a+2b)(a-2b)
=a²+4ab-(a²-4b²)
=4ab+4b²
=4b(a+b)
=0
38.9²-2×38.9×48.9+48.9²
=(38.9-48.9)²
=(-10)²
=100
24²+24×32+16²
=24²+2×24×16+16²
=(24+16)²
=40²
=1600
M=x²+y²,N=2xy
M-N=x²+y²-2xy=(x-y)²≥0
∴M≥N (当x=y时取等号
a²+2ab+b²=0
即(a+b)²=0
∴a+b=0
∴a(a+4b)-(a+2b)(a-2b)
=a²+4ab-(a²-4b²)
=4ab+4b²
=4b(a+b)
=0