Tính :

a) 1+2+3+...+9999

b) 1+5+9+...1001

c) 1/2 . 2/3 . 3/4 . ... . 99/100

3,7-\(\left|x-4,5\right|=0\)

\(\left(4x-3\right)\left(x-0,7\right)=0\)

Tìm tổng :

\(\dfrac{1}{1.3}+\dfrac{1}{3.5}+...+\dfrac{1}{\left(2n-1\right).\left(2n+1\right)}+...+\dfrac{1}{255.257}\)

S= 2^2 + 4^2 + 6^2 + ... + 20^2

bài 1 :

a)\(\dfrac{3}{7}\) + ( -\(\dfrac{5}{2}\) ) + ( \(\dfrac{-3}{5}\) ) b) ( -\(\dfrac{4}{3}\) ) + (-\(\dfrac{2}{5}\) ) + (- \(\dfrac{3}{2}\) )

c) \(\dfrac{4}{5}\)- ( \(\dfrac{-2}{7}\) ) - ( \(\dfrac{7}{10}\) ) d ) \(\dfrac{2}{3}\) - [(-\(\dfrac{4}{7}\) ) - ( \(\dfrac{1}{2}\) + \(\dfrac{3}{8}\) )]

bài 2 : tìm x , biêt

a) x + \(\dfrac{1}{3}\) = \(\dfrac{3}{4}\) ; b) x- \(\dfrac{2}{5}\) = \(\dfrac{5}{7}\)

c) -x - \(\dfrac{2}{3}\) = - \(\dfrac{6}{7}\) d) \(\dfrac{4}{7}\) -x = \(\dfrac{1}{3}\)

( mai nộp bài rôi ai giúp vs )

7:4.x+3:2=-2:5

(5x-1)(2x-1:3=0

tìm x, y thuộc Z

a, 3x=2y ; 5y=7z và 3x+5y-7z=60

b. \(\dfrac{x}{2}\) = \(\dfrac{y}{3}\)= \(\dfrac{z}{4}\) và x2 + y2 +z2 = 116

\(\dfrac{6}{7}\):(\(\dfrac{1}{3}\)-\(\dfrac{-5}{2}\))\(^2\)

tính (0,25)4.1024

tìm x

a/ \(\dfrac{5^x}{125}\)= 25\(^4\) b/ \(\dfrac{3^x}{3}\)+ 3\(^{x-2}\) = 4

c/ (x + \(\dfrac{2006}{2007}\))\(^6\) =0 d/ (x-\(\dfrac{1}{5}\))\(^3\)= \(\dfrac{8}{125}\)

e/ 3\(^x\) + 3\(^{x-2}\)= 810 g/ 5\(^{x+2}\) +5\(^{x+1}\) +5\(^x\) = 19375

giúp mk nha các bn mk