Toán Tính tổng: 10/56 + 10/140 +10/260 + …………. + 10/1400 06/10/2021 By Kennedy Tính tổng: 10/56 + 10/140 +10/260 + …………. + 10/1400
Đáp án:gọi tổng này là A A=10/56+10/140+10/260+…..+10/1400 A=5/28+5/70+5/130+……+5/700 3A/5=3/4.7+3/7.10+3/10.13+……+3/25.28 3A/5=1/4-1/7+1/7-1/10+1/10-1/13+…….+1/25-1/28 3A/5=1/4-1/28 3A/5=3/14 A=3/14: 3/5 A=5/14 Vaayj A=5/14 Trả lời
Đáp án:gọi tổng này là A
A=10/56+10/140+10/260+…..+10/1400
A=5/28+5/70+5/130+……+5/700
3A/5=3/4.7+3/7.10+3/10.13+……+3/25.28
3A/5=1/4-1/7+1/7-1/10+1/10-1/13+…….+1/25-1/28
3A/5=1/4-1/28
3A/5=3/14
A=3/14: 3/5
A=5/14
Vaayj A=5/14
=5/14