Đáp án:
mik lm phần a nhé còn lại bn dựa theo mà lm nhé
a) 3A = 3^2 + 3^3 + 3^4 + ... + 3^2009
=> 3A - 2A = 3^2 + 3^3 + 3^4 + ... + 3^2009 - ( 3 + 3^2 + 3^3 + ... + 3^2008 )
=> 2A = 3^2009 - 3
=> A = ( 3^2009 - 3)/2
Làm giúp mình với!\(\left(1-\frac{1}{1X2}\right)+\left(1-\frac{1}{2X3}\right)+...+\left(1-\frac{1}{29X30}\right)\)
a) âm 3 phần 2 - 2x + 3 phần 4 = - 2
b) ( âm 2 phần 3 x - 3 phần 5 )(3 phần âm 2 - 10 phần 3 ) = 2 phần 5
Giúp mik vs
c )\(\dfrac{x}{2}-\left(\dfrac{3x}{5}-\dfrac{13}{5}\right)=-\left(\dfrac{7}{5}+\dfrac{7}{10}.x\right)\)
d)\(\dfrac{2x-3}{3}+\dfrac{-3}{2}=\dfrac{5-3x}{6}-\dfrac{1}{3}\)
\(\dfrac{2x-3}{3}+\dfrac{-3}{2}=\dfrac{5-3x}{6}-\dfrac{1}{3}\)
e) \(\dfrac{3}{3x}-\dfrac{3}{12}=\dfrac{4}{5}-\left(\dfrac{7}{x}-2\right)\)
f) \(\dfrac{1}{x-1}+\dfrac{-2}{3}\left(\dfrac{3}{4}-\dfrac{6}{5}\right)=\dfrac{5}{2-2x}\)
g) \(3-\dfrac{2}{2x-3}=\dfrac{2}{5}=\dfrac{2}{9-6x}-\dfrac{3}{2}\)
h) \(\dfrac{x}{2}-\dfrac{1}{x}=\dfrac{1}{12}\)
i) \(x^2-\dfrac{7}{6}x+\dfrac{1}{3}=0\)
k) \(\dfrac{13}{x-1}+\dfrac{5}{2x-2}-\dfrac{6}{3x-3}\)
m) \(\left(\dfrac{3}{2}-\dfrac{2}{-5}\right):x-\dfrac{1}{2}=\dfrac{3}{2}\)
n) \(\left(\dfrac{3}{2}-\dfrac{5}{11}-\dfrac{3}{13}\right)\left(2x-2\right)=\left(-\dfrac{3}{4}+\dfrac{5}{22}+\dfrac{3}{26}\right)\)
\(3-\dfrac{2}{2x-3}=\dfrac{2}{5}+\dfrac{2}{9-6x}-\dfrac{3}{2}\)
h) \(\dfrac{x}{2}-\dfrac{1}{x}=\dfrac{1}{12}\)
i) \(x^2-\dfrac{7}{6}x+\dfrac{1}{3}=0\)
k) \(\dfrac{13}{x-1}+\dfrac{5}{2x-2}-\dfrac{6}{3x-3}\)
Tính bằng cách hợp lí :
S= 3/4 - 0,25 - [ 7/3 + ( -9/2 )] - 5/6
Giúp mình với
Tính nhanh
\(\dfrac{1}{3}\) - \(\dfrac{3}{4}\) - \(\left(\dfrac{-3}{5}\right)\) + \(\dfrac{1}{64}\) - \(\dfrac{2}{9}\) -\(\dfrac{1}{36}\) + \(\dfrac{1}{15}\)
