1) 745 + 744 - 742 = 742(73+72-1) = 391.742 => đpcm
2) 325 + 323 - 321 = 321(34 + 32 - 1) = 321.89 => đpcm
1/ 745+744-742
=>742(73+72-1)
=>742.391
Vì 391\(⋮\)391
=>742.391\(⋮\)391
=>745+744-742\(⋮\)391
(đpcm)
2/ Ta có:
325+323-321
=>321(34+32-1)
=>321.89
Vì 89\(⋮\)89=>321.89\(⋮\)89
=>325+323-321\(⋮\)89
(đpcm)
1) Ta có :742.(73 + 72 - 1) = 742.391 \(⋮\)391
=> 745 + 744 - 742 \(⋮\)391
2) Ta có : 325 + 323 - 321 = 321.(34 + 32 - 1)
=321 . 89\(⋮\)89
=>325 + 323 - 321 \(⋮\) 89