Tính :
Giải thích
27+35=1035+2135=31353135-27=3135-2×57×5=3135-1035=21353135-35=3135-3×75×7=3135-2135=103535+27≡3×75×7+2×57×5=2135+1035=3135
27+35=1035+2135=31353135-27=3135-2×57×5=3135-1035=21353135-35=3135-3×75×7=3135-2135=103535+27≡3×75×7+2×57×5=2135+1035=3135