Tính nhanh:
1) 127^2+146.127+73^2
2) 9^8.2^8-(18^4-1).(18^4+1)
3) 100^2-99^2+98^2=97^2+…+2^2-1^2
4) 780^2….220^2/125^2+150.125+75^2
Tính nhanh: 1) 127^2+146.127+73^2 2) 9^8.2^8-(18^4-1).(18^4+1) 3) 100^2-99^2+98^2=97^2+…+2^2-1^2 4) 780^2….220^2/125^2+150.125+75^2
By Mary
1, 127² + 146.127 + 73²
= 127² + 2.127.73 + 73²
= (127 + 73)²
= 200²
=20000
2, 9^8.2^8-(18^4-1).(18^4+1)
= 18^8 – (18^8 -1)
= 18^8 – 18^8 +1
=1
3, 100² – 99² + 98² – 97² +…+2²-1²
=(100²-99²) + (98²-97²) + …+ (2²-1²)
=(100-99)(100+99) + (98-97)(98+97) + …+ (2-1)(2+1)
=100+99+98+97+…+2+1
=(100+1).100/2
=5050