1) 78²-26²+52²=(78-26)(78+26)+52²=52·104-52²=2·52²-52²=52²
2) 340²-336²=(340-336)(340+336)=4·676=2²·26²=52²
3) 52²/52²=1
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1) 54²+54·70+35²=54²+2·54·35+35²=(54+35)²=89²
2) (47-42)²+4·47·42=47²+2·47·42+42²=(47+42)²=89²
3) 89²/89²=1