1/1*2 + 1/2*3 +1/3*4 +.....+ 1/x(x+1) =499/500
Hãy tìm x
Những câu hỏi liên quan
Tìm X:
1/1 x 2 +1/2 x 3+ 1/3 x 4 + .........+1/ X x ( X +1) = 499/500
giải chi tiết gúp mình với ,cô sắp kểm tra rùi !!!!!!!!!!!!!!!
ta có:
1-1/2+1/2-1/3+1/3-1/4+....+1/x -1/x+1 =499/500
1-1/x+1 =499/500
1/x+1 =1/500
x+1=500
x=499
\(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{X\times\left(X+1\right)}=\frac{499}{500}\)
\(\Leftrightarrow1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{X}-\frac{1}{X+1}=\frac{499}{500}\)
\(\Leftrightarrow1-\frac{1}{X+1}=\frac{499}{500}\)
\(\Leftrightarrow\frac{1}{X+1}=\frac{1}{500}\)
\(\Leftrightarrow X+1=500\)
\(\Leftrightarrow X=499\)
1, Tính:
a) -287 + 499 + (-499) + 285
b) 1992 + (-53) + 158 + (-247) + (-1592)
c) 15 x (2 x 3\(^2\) - 4\(^2\)) + (7 x 2\(^0\)- 1) x (5\(^5\) : 5\(^4\) + 10\(^1\))
b: Ta có: \(1992+\left(-53\right)+158+\left(-247\right)+\left(-1592\right)\)
\(=\left(1992-1592\right)+\left(-53-247\right)+158\)
\(=400-300+158=258\)
Đúng 1
Bình luận (0)
1/1*2+1/2*3+1/3*4+............+1/x(x+1)=499/500
Tìm x thuộc z : 1/3+1/6+1/10+...+2/x(x+1)=499/1000
\(\frac{1}{3}+\frac{1}{6}=\frac{1}{10}+...+\frac{2}{x\left(x+1\right)}=\frac{499}{1000}\)
\(\frac{2}{6}+\frac{2}{12}+...+\frac{2}{x\left(x+1\right)}=\frac{499}{1000}\)
\(\frac{2}{2.3}+\frac{2}{3.4}+...+\frac{2}{x\left(x+1\right)}=\frac{499}{1000}\)
\(2\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{x\left(x+1\right)}\right)=\frac{499}{1000}\)
\(2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{499}{1000}\)
\(2\left(\frac{1}{2}-\frac{1}{x-1}\right)=\frac{499}{1000}\)
\(\frac{1}{2}-\frac{1}{x-1}=\frac{499}{2000}\)
\(\frac{2000\left(x-1\right)}{2\left(x-1\right)2000}-\frac{2.2000}{\left(x-1\right)2.2000}=\frac{499.2\left(x-1\right)}{2000.2\left(x-1\right)}\)
Khử mẫu
\(2000x-2000-4000=998x-998\)
\(2000x-6000=998x-998\)
\(1002x-5002=0\)
\(1002x=5002\Leftrightarrow x=\frac{2501}{501}\)
Tìm x biết : 1/3+1/6+1/10+...+2/x.(x+1)=499/1000
Giúp mình nhé! :))))
theo bai co 1/3+1/6+...+2/x.x+1=499/1000
(=)2/2.3+2/3.4+...+2/x.(x+1)=499/1000
(=)2(1/2-...-1/x+1)=499/1000
(=)1/2-1/x+1=499/2000
(=)1/x+1=501/2000
den day thi minh chiu roi!
Đúng 0
Bình luận (0)
1)tìm x biết
(1/1*2+1/2*3+1/3*4+...+1/x*x+1)=499/500
2)khi nhân 1 số với 9,05.1 bạn đã sơ ý quên viết số 0 của số 9,05 nên tích tăng thêm 5,76 đơn vị so với tích đúng.tìm tích đúng
\(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-....-\frac{1}{x+1}=\frac{499}{500}\)
1 - 499/500 = 1/x + 1
1/500 = 1/x+1
x + 1 = 500
x = 499
Đúng 0
Bình luận (0)
bài 1:tìm X
phần a, 1/1x2 + 1/ 2x 3 + 1/ 3 x4 + ....+ 1/ X x( X +1)= 499 / 500
phần b,1/1x3 + 1/3x5 + 1/ 5 x 7+ ....+ 1/X x ( X + 2 )= 20 /41
a) 1/1.2 + 1/2.3 + 1/3.4 + .... + 1/x.(x+1) = 499/500
1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + .... + 1/x - 1/x+1 = 499/500
1 - 1/x+1 = 499/500
1/x+1 = 1 - 499/500
1/x+1 = 1/500
x + 1 = 500
x = 500 - 1
x = 499
b) 1/1.3 + 1/3.5 + 1/5.7 + .... + 1/x.(x+2) = 20/41
1/2 . [ 2/1.3 + 2/3.5 + 2/5.7 + ... + 2/x.(x+2) ] = 20/41
1/2 . [ 1 - 1/3 + 1/3 - 1/5 + 1/5 - 1/7 + ... + 1/x - 1/x+2 ] = 20/41
1/2 . [ 1 - 1/x+2 ) = 20/41
1 - 1/x+2 = 20/41 : 1/2
1 - 1/x+2 = 40/41
1/x+2 = 1 - 40/41
1/x+2 = 1/41
x + 2 = 41
x = 41 - 2
x = 39
Đúng 0
Bình luận (0)
1.1/2+1.2/3+1/3.4+1/4.5+..+1/x(x+1)=499/500
\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+...+\dfrac{1}{x.\left(x+1\right)}=\dfrac{499}{500}\)
\(\Leftrightarrow1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{x}-\dfrac{1}{x+1}=\dfrac{499}{500}\)
\(\Leftrightarrow1-\dfrac{1}{x+1}=\dfrac{499}{500}\)
\(\Leftrightarrow x=499\)
Đúng 1
Bình luận (0)
Xem thêm câu trả lời
A.3^x=243 B.4^x=4096 C. 5^3-x=25 D.8^2x-3=512 E.2214-5.7^2x-3=499 J. 2^x+3+2^x+1=80
a: 3^x=243
=>3^x=3^5
=>x=5
b: 4^x=4096
=>4^x=4^5
=>x=5
c: 5^3-x=25
=>3-x=2
=>x=1
d: =>2x-3=3
=>2x=6
=>x=3
j: =>2^x*8+2^x*2=80
=>2^x=8
=>x=3
Đúng 0
Bình luận (0)