Câu hỏi của ichigo nguyệt love

Question

(31-1)(-1/2x+5)=0

x-20/11-20/13.15-20/15.17-...........-22/53.55=3/11

tìm x nhé các bn

bn nào giúp mk sẽ tick cho 3 tick

yêu các bn nhìu

Quìn · Accepted Answer

a) $\left(31-1\right)\left(\dfrac{-1}{2}x+5\right)=0$

$30\left(\dfrac{-1}{2}x+5\right)=0$

$\left(\dfrac{-1}{2}x+5\right)=0:30$

$\dfrac{-1}{2}x+5=0$

$\dfrac{-1}{2}x=0-5$

$\dfrac{-1}{2}x=-5$

$x=-5:\dfrac{-1}{2}$

$x=10$

b) $x-\dfrac{20}{11.13}-\dfrac{20}{13.15}-\dfrac{20}{15.17}-...-\dfrac{20}{53.55}=\dfrac{3}{11}$

$x-10\left(\dfrac{2}{11.13}+\dfrac{2}{13.15}+\dfrac{2}{15.17}+...+\dfrac{2}{53.55}\right)=\dfrac{3}{11}$

$x-10\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+\dfrac{1}{15}-\dfrac{1}{17}+...+\dfrac{1}{53}-\dfrac{1}{55}\right)=\dfrac{3}{11}$

$x-10\left(\dfrac{1}{11}-\dfrac{1}{55}\right)=\dfrac{3}{11}$

$x-10.\dfrac{4}{55}=\dfrac{3}{11}$

$x-\dfrac{8}{11}=\dfrac{3}{11}$

$x=\dfrac{3}{11}+\dfrac{8}{11}=1$Câu trả lời: a) $\left(31-1\right)\left(\dfrac{-1}{2}x+5\right)=0$