Cho B = 12/(2.4)2 + 20/(4.6)2 + … 388/(96.98)2 + 396/(98.100)2. Hãy so sánh B với 1/4 03/10/2021 Bởi Adalynn Cho B = 12/(2.4)2 + 20/(4.6)2 + … 388/(96.98)2 + 396/(98.100)2. Hãy so sánh B với 1/4
B = 12/(2.4)2 + 20/(4.6)2 + … 388/(96.98)2 + 396/(98.100)2 B = 4.2-2.2/(2.4)2 + 6.2-4.2/(4.6)2 + … 98.2-96.2/(96.98)2 + 100.2-98.2/(98.100)2 B = 1/2.2-1/4.2+1/4.2-1/6.2+1/6.2+…-1/98.2+1/98.2-1/100.2 B=1/2.2-1/100.2=1/4-1/100.2<1/4 ⇔ B<1/4 Bình luận
B = 12/(2.4)2 + 20/(4.6)2 + … 388/(96.98)2 + 396/(98.100)2 B = (2.2+4.2)/(2.4)2 + (4.2+6.2)/(4.6)2 + … (96.2+98.2)/(96.98)2 + (98.2+100.2)/(98.100)2 B = 2.2/(2.4)2+4.2/(2.4)2 + 4.2/(4.6)2+6.2/(4.6)2 + … + 96.2/(96.98)2+98.2/(96.98)2 +98.2/(98.100)2+100.2/(98.100)2 B = 1/4+1/2+1/6+1/4+…+1/98+1/96+1/100+1/98>1/4 Vậy B>1/4 Bình luận
B = 12/(2.4)2 + 20/(4.6)2 + … 388/(96.98)2 + 396/(98.100)2
B = 4.2-2.2/(2.4)2 + 6.2-4.2/(4.6)2 + … 98.2-96.2/(96.98)2 + 100.2-98.2/(98.100)2
B = 1/2.2-1/4.2+1/4.2-1/6.2+1/6.2+…-1/98.2+1/98.2-1/100.2
B=1/2.2-1/100.2=1/4-1/100.2<1/4
⇔ B<1/4
B = 12/(2.4)2 + 20/(4.6)2 + … 388/(96.98)2 + 396/(98.100)2
B = (2.2+4.2)/(2.4)2 + (4.2+6.2)/(4.6)2 + … (96.2+98.2)/(96.98)2 + (98.2+100.2)/(98.100)2
B = 2.2/(2.4)2+4.2/(2.4)2 + 4.2/(4.6)2+6.2/(4.6)2 + … + 96.2/(96.98)2+98.2/(96.98)2 +98.2/(98.100)2+100.2/(98.100)2
B = 1/4+1/2+1/6+1/4+…+1/98+1/96+1/100+1/98>1/4
Vậy B>1/4