( 1/1.7+1/7.13+1/13.19+……+1/85.91)+125x=-110/91 HELP ME!!! 05/11/2021 Bởi Nevaeh ( 1/1.7+1/7.13+1/13.19+……+1/85.91)+125x=-110/91 HELP ME!!!
Đáp án: $x=-\dfrac{1}{91}$ Giải thích các bước giải: Ta có :$(\dfrac{1}{1.7}+\dfrac{1}{7.13}+\dfrac{1}{13.19}+..+\dfrac{1}{85.91})+125x=-\dfrac{110}{91}$ $\to \dfrac16(\dfrac{6}{1.7}+\dfrac{6}{7.13}+\dfrac{6}{13.19}+..+\dfrac{6}{85.91})+125x=-\dfrac{110}{91}$ $\to \dfrac16(\dfrac{7-1}{1.7}+\dfrac{13-7}{7.13}+\dfrac{19-13}{13.19}+..+\dfrac{91-85}{85.91})+125x=-\dfrac{110}{91}$ $\to \dfrac16(\dfrac11-\dfrac17+\dfrac17-\dfrac1{13}+\dfrac1{13}-\dfrac1{19}+..+\dfrac{1}{85}-\dfrac{1}{91})+125x=-\dfrac{110}{91}$ $\to \dfrac16(1-\dfrac{1}{91})+125x=-\dfrac{110}{91}$ $\to \dfrac16\cdot \dfrac{90}{91}+125x=-\dfrac{110}{91}$ $\to \dfrac{15}{91}+125x=-\dfrac{110}{91}$ $\to 125x=-\dfrac{125}{91}$ $\to x=-\dfrac{1}{91}$ Bình luận
Đáp án: Giải thích các bước giải: ( $\frac{1}{1.7}$ + $\frac{1}{7.13}$ + $\frac{1}{13.19}$ +….+ $\frac{1}{85.91}$ ) +125x = $\frac{-110}{91}$ 6. ( $\frac{6}{1.7}$ + $\frac{6}{7.13}$ + $\frac{6}{13.19}$ +…+ $\frac{6}{85.91}$ ) + 125x = $\frac{-660}{91}$. 6 ($\frac{1}{1}$ – $\frac{1}{7}$ + $\frac{1}{7}$ – $\frac{1}{13}$ + ….+ $\frac{1}{85}$ – $\frac{1}{91}$ ) 125x = $\frac{-660}{91}$ ($\frac{1}{1}$ – $\frac{1}{91}$ ) + 125x = $\frac{-660}{91}$ $\frac{90}{91}$ +125x = $\frac{-660}{91}$ 125x = $\frac{-660}{91}$ – $\frac{90}{91}$ 125x = $\frac{-750}{91}$ x = $\frac{-750}{91}$ : 125 x = $\frac{-6}{91}$ Bình luận
Đáp án: $x=-\dfrac{1}{91}$
Giải thích các bước giải:
Ta có :
$(\dfrac{1}{1.7}+\dfrac{1}{7.13}+\dfrac{1}{13.19}+..+\dfrac{1}{85.91})+125x=-\dfrac{110}{91}$
$\to \dfrac16(\dfrac{6}{1.7}+\dfrac{6}{7.13}+\dfrac{6}{13.19}+..+\dfrac{6}{85.91})+125x=-\dfrac{110}{91}$
$\to \dfrac16(\dfrac{7-1}{1.7}+\dfrac{13-7}{7.13}+\dfrac{19-13}{13.19}+..+\dfrac{91-85}{85.91})+125x=-\dfrac{110}{91}$
$\to \dfrac16(\dfrac11-\dfrac17+\dfrac17-\dfrac1{13}+\dfrac1{13}-\dfrac1{19}+..+\dfrac{1}{85}-\dfrac{1}{91})+125x=-\dfrac{110}{91}$
$\to \dfrac16(1-\dfrac{1}{91})+125x=-\dfrac{110}{91}$
$\to \dfrac16\cdot \dfrac{90}{91}+125x=-\dfrac{110}{91}$
$\to \dfrac{15}{91}+125x=-\dfrac{110}{91}$
$\to 125x=-\dfrac{125}{91}$
$\to x=-\dfrac{1}{91}$
Đáp án:
Giải thích các bước giải:
( $\frac{1}{1.7}$ + $\frac{1}{7.13}$ + $\frac{1}{13.19}$ +….+ $\frac{1}{85.91}$ ) +125x = $\frac{-110}{91}$
6. ( $\frac{6}{1.7}$ + $\frac{6}{7.13}$ + $\frac{6}{13.19}$ +…+ $\frac{6}{85.91}$ ) + 125x = $\frac{-660}{91}$. 6
($\frac{1}{1}$ – $\frac{1}{7}$ + $\frac{1}{7}$ – $\frac{1}{13}$ + ….+ $\frac{1}{85}$ – $\frac{1}{91}$ ) 125x = $\frac{-660}{91}$
($\frac{1}{1}$ – $\frac{1}{91}$ ) + 125x = $\frac{-660}{91}$
$\frac{90}{91}$ +125x = $\frac{-660}{91}$
125x = $\frac{-660}{91}$ – $\frac{90}{91}$
125x = $\frac{-750}{91}$
x = $\frac{-750}{91}$ : 125
x = $\frac{-6}{91}$