(2.x+1)-7=14
\(\frac{1}{2}\cdot\frac{18}{14}+\frac{1}{2}\cdot\frac{3}{14}-\frac{1}{2}\cdot\frac{7}{14}\)
\(=\frac{1}{2}\left(\frac{18}{14}+\frac{3}{14}-\frac{7}{14}\right)\)
\(=\frac{1}{2}\cdot1=\frac{1}{2}\)
1/Tính :
a. A= 1/17+ 7/17.27 + 7/27.37 + .................... +7/1997.2007
b. B=-1/2007.2006 - 1/2005.2006 - 1/2005.2004 - .................... - 1/3.2 - 1/2.1
2/Tim x biết :
2/(x+2)(x+4) + 4/(x+4)(x+8) + 6/(x+8)(x+14) = x/(x+2)(x+14)
Với x không thuộc tập hợp {-2;-4;-6;-8;-14}
A = 7/7.17 + 7/17.27 + 7/27.37 + ............ +7/1997.2007
A=7/10 ( 10/7.17 + 10/17.27 + 10/27.37 + ................+10/1997.2007)
A= 7/10 ( 1/7 -1/17 + 1/17 - 1/27 + 1/27 - 1/37 +...............+ 1/1997 - 1/2007)
A= 7/10 (1/7 - 1/2007)
A= 7/10 . 2000/14049
A=200/2007
bây h mk có vc rùi tích đúng nha tối mk lm típ cho
| 7 - 3/4 . x | - 3/2 = 1/1/2
5 - | x - 3 | = 5
| 7/2 - 42 | + 14 = 14
2/3 - | x + 2 | = 2
5/6 . | 3 - x | + 4 = 2
Giải giúp mình với
|7 - \(\dfrac{3}{4}\)\(x\)| - \(\dfrac{3}{2}\) = \(\dfrac{1}{\dfrac{1}{2}}\)
|7 - \(\dfrac{3}{4}x\)| - \(\dfrac{3}{2}\) = 2
|7 - \(\dfrac{3}{4}\)\(x\)| = 2 + \(\dfrac{3}{2}\)
|7 - \(\dfrac{3}{4}x\)| = \(\dfrac{7}{2}\)
\(\left[{}\begin{matrix}7-\dfrac{3}{4}x=\dfrac{7}{2}\\7-\dfrac{3}{4}x=-\dfrac{7}{2}\end{matrix}\right.\)
\(\left[{}\begin{matrix}\dfrac{3}{4}x=7-\dfrac{7}{2}\\\dfrac{3}{4}=7+\dfrac{7}{2}\end{matrix}\right.\)
\(\left[{}\begin{matrix}\dfrac{3}{4}x=\dfrac{7}{2}\\\dfrac{3}{4}x=\dfrac{21}{2}\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=\dfrac{14}{3}\\x=14\end{matrix}\right.\)
5 - |\(x-3\)| = 5
|\(x-3\)| = 5 - 5
|\(x-3\)| = 0
\(x-3\) = 0
\(x\) = 3
|\(\dfrac{7}{2}\) - 42| + 14 = 14 ( vô lý xem lại đề bài nhé em)
\(\dfrac{2}{3}\) - |\(x+2\)| = 2
|\(x+2\)| = \(\dfrac{2}{3}\) - 2
|\(x+2\)| = - \(\dfrac{4}{3}\)
|\(x+2\)| ≥ 0 ∀ \(x\)
Vậy \(x\in\) \(\varnothing\)
|0,75x - 1/5| + 4/7= 1 và 4/7
1/2+1/14+1/35+...+1/x(x+3:2=9/14
tính nhanh 5/14 x 2/9 + 5/14 + 5/14 x 7/9, 6/8 : 7/6 - 6/8 : 1/6
a: \(=\dfrac{5}{14}\left(\dfrac{2}{9}+\dfrac{7}{9}+1\right)=\dfrac{5}{14}\cdot2=\dfrac{5}{7}\)
b: \(=\dfrac{6}{8}\left(\dfrac{6}{7}-6\right)=\dfrac{6}{8}\cdot\dfrac{-36}{7}=\dfrac{-216}{56}=\dfrac{-27}{7}\)
Tìm x, biết: x + 2/7=1/2
A.x= 3/14 B. x=2/14 C. x=13/3 D. x=1/5.
X+\(\dfrac{2}{7}\)=\(\dfrac{1}{2}\)
X = \(\dfrac{1}{2}\)-\(\dfrac{2}{7}\)
X = \(\dfrac{3}{14}\)
Chọn đáp án A. \(\dfrac{3}{14}\)
Tìm x: \(1\frac{1}{7}-\frac{5}{7}< \frac{x}{7}< 2\frac{1}{14}-1\frac{3}{14}\)
\(1\frac{1}{7}-\frac{5}{7}< \frac{x}{7}< 2\frac{1}{14}-1\frac{3}{14}\)
=> \(\frac{8}{7}-\frac{5}{7}< \frac{x}{7}< \frac{29}{14}-\frac{17}{14}\)
=> \(\frac{3}{7}< \frac{x}{7}< \frac{12}{14}\)
=> \(\frac{3}{7}< \frac{x}{7}< \frac{6}{7}\)
=> 3 < x < 6
=> x thuộc { 3 ; 4 ; 5 ; 6 }
7 x 1 x 7 x 7 x 2 + 14 + 7 x 3 + 21 =
Bài 1 :Tìm x:
|0,75x - 1/5|+4/7=1 và 4/7
Bài 2 : Tính:
1/2+1/14+1/35+...+1/x (x + 3)÷2=9/14
( 2 x y + 2/15 ) x 3 = 4/5
7/9 x ( 2 - 1/3 x y ) = 14/15
4/21 + 5 x y - 8/7 = 1/3
7/12 x y - 3/12 x y = 5
6/7 x y + 14/36 + 1/7 x y = 7/18
Giúp em với ạ
( 2 x y + 2/15 ) x 3 = 4/5
( 2 x y + 2/15 ) = 4/5 : 3
( 2 x y + 2/15 ) = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 :2
y = 1/15
(2 x y + 2/15) x 3 = 4/5
2 x y + 2/15) = 4/5 : 3
2 x y + 2/15 = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 : 2
y = 1/15
7/9 x (2 - 1/3 x y) = 14/15
(2 - 1/3 x y) = 14/15 : 7/9
(2 - 1/3 x y) = 6/5
2 - y = 6/5 x 1/3
2 - y = 2/5
y = 2/5 + 2
y = 12/5
4/21 + 5 x y - 8/7 = 1/3
4/21 + 5 x y = 1/3 + 8/7
4/21 + 5 x y = 31/21
5 x y = 31/21 - 4/21
5 x y = 9/7
y = 9/7 : 5
y = 9/35
7/12 x y - 3/12 x y = 5
y x (7/12 - 3/12) = 5
y x 1/3 = 5
y = 5 : 1/3
y = 15