3 mũ 2/10+ 3 mũ 2/40+3 mũ 2/88+……+3 mũ 2/340 02/09/2021 Bởi Piper 3 mũ 2/10+ 3 mũ 2/40+3 mũ 2/88+……+3 mũ 2/340
Đáp án: 3mu2/10+3mu2/40+3mu2/88+...+3mu2/340 9/2⋅5+9/5⋅8+9/8⋅11+...+9/17⋅20 9/3(3/2⋅5+3/5⋅8+3/8⋅11+...+3/17⋅20) 3(1/2−1/5+1/5−1/8+1/8−1/11+...+1/17−1/20) 3(1/2−1/20)=3(10/20−1/20)=3⋅9/20=27/20 xong rùi nek Bình luận
`(3^2)/10 + (3^2)/40 + (3^2)/88 + … + (3^2)/340` `= ( 3/(2.5) + 3/(5.8) + 3/(8.11) + …. + 3/(17.20) ) . 3` `= ( 1/2 – 1/5 + 1/5 – 1/8 + 1/8 – 1/11 + … + 1/17 – 1/20 ) . 3` `= ( 1/2 – 1/20 ) . 3` `= 9/20 . 3` `= 27/20` Bình luận
Đáp án:
3mu2/10+3mu2/40+3mu2/88+...+3mu2/340
9/2⋅5+9/5⋅8+9/8⋅11+...+9/17⋅20
9/3(3/2⋅5+3/5⋅8+3/8⋅11+...+3/17⋅20)
3(1/2−1/5+1/5−1/8+1/8−1/11+...+1/17−1/20)
3(1/2−1/20)=3(10/20−1/20)=3⋅9/20=27/20
xong rùi nek
`(3^2)/10 + (3^2)/40 + (3^2)/88 + … + (3^2)/340`
`= ( 3/(2.5) + 3/(5.8) + 3/(8.11) + …. + 3/(17.20) ) . 3`
`= ( 1/2 – 1/5 + 1/5 – 1/8 + 1/8 – 1/11 + … + 1/17 – 1/20 ) . 3`
`= ( 1/2 – 1/20 ) . 3`
`= 9/20 . 3`
`= 27/20`