Tính giá trị biểu thức B= 2/ 35 + 4/77 + 2/ 143 + 4/ 221 + 2/ 323 + 4/ 437 + 2/ 575
Giải thích
B=235+477+2143+4221+2322+4437+2575
=25×7+47×11+211×13+413×17+217×19+419×23+223×25
=15−17+17−111+111−113+113−117+117−119+119−123+123−125
=15−125=425
B=235+477+2143+4221+2322+4437+2575
=25×7+47×11+211×13+413×17+217×19+419×23+223×25
=15−17+17−111+111−113+113−117+117−119+119−123+123−125
=15−125=425