\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+....+\dfrac{1}{38.39}=\dfrac{5}{3}-x\)
=> \(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+......+\dfrac{1}{38}-\dfrac{1}{39}=\dfrac{5}{3}-x\)
=> \(1-\dfrac{1}{39}=\dfrac{5}{3}-x\)
=> \(\dfrac{39}{39}-\dfrac{1}{39}=\dfrac{65}{39}-\dfrac{39x}{39}\)
=> 39-1=65-39x
=> 38=65-39x
=> 39x=-38+65
=> 39x=27
=> x=\(\dfrac{9}{13}\)
vậy x= \(\dfrac{9}{13}\)
a.1/3 + -1/4 + 2/5.mấy cái dấu gạch này / là cho dấu phân số nha
b.1/3 + -4/5 + 16/12
c.1/2 + 1/6+-1/4 + 1/5
tìm X biết
a. x + 1/9 - 3/5=3/6
b. 3/4 - x + 6/11 = 5/6
c.x-1/3=1/7
d.1/15-x=3/10
e.x-1/24=5/8-1/3
f.4/10-x=-3/20 + 3/5
g.x/4-3/7 + 2/5 = 31/140
h.5/12 + 5/x - 1/8 = 1/2
Tìm x: a) 3/4 - x =1 b) x + 4 = 1/5 c) x - 1/5 = 2 d) x + 5/3 = 1/81
Tìm x, biết:
a) 3/4 - x = 1
b) x + 4 = 1/5
c) x - 1/5 = 2
d) x + 5/3 = 1/81
Tính :
a) \(\dfrac{3}{5}-\dfrac{-7}{10}-\dfrac{13}{-20}\)
b) \(\dfrac{3}{4}+\dfrac{-1}{3}-\dfrac{5}{18}\)
c) \(\dfrac{3}{14}-\dfrac{5}{-8}+\dfrac{-1}{2}\)
d) \(\dfrac{1}{2}+\dfrac{1}{-3}+\dfrac{1}{4}-\dfrac{-1}{6}\)
a) Tính :
\(1-\dfrac{1}{2};\dfrac{1}{2}-\dfrac{1}{3};\dfrac{1}{3}-\dfrac{1}{4};\dfrac{1}{4}-\dfrac{1}{5};\dfrac{1}{5}-\dfrac{1}{6}\)
b) Sử dụng kết quả của câu a) để tính nhanh tổng sau :
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}\)
Tìm \(x\) biết :
a) \(x-\dfrac{3}{4}=\dfrac{1}{2}\)
b) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)
1)\(\dfrac{-3}{4}\)-x=0.25
2)x:4\(\dfrac{1}{3}\)=-2.5
bài 1 : tìm x:
4(x−\(\dfrac{1}{4}\) )−3(x+\(\dfrac{2}{3}\) )=0
Tìm x, biết: 1/2 - |x-3| : 2 = 1
