{1/15 + 1/35+1/65} x x = 1
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Những câu hỏi liên quan
18 tháng 3 2023
a: \(\Leftrightarrow\dfrac{32}{x}=\dfrac{2}{15}+\dfrac{2}{35}+...+\dfrac{2}{99}\)
=>32/x=1/3-1/5+1/5-1/7+...+1/9-1/11
=>32/x=1/3-1/11=8/33
=>x=32:8/33=132
b: \(\Leftrightarrow1-\dfrac{1}{6}+1-\dfrac{1}{12}+...+1-\dfrac{1}{56}=\dfrac{x}{16}\)
\(\Leftrightarrow6-\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{7}-\dfrac{1}{8}\right)=\dfrac{x}{16}\)
=>x/16=6-1/2+1/8=11/2+1/8=45/8=90/16
=>x=90
c: \(\Leftrightarrow\dfrac{22}{x}=\left(1-\dfrac{1}{2}\right)\left(1+\dfrac{1}{2}\right)\cdot\left(1-\dfrac{1}{3}\right)\left(1+\dfrac{1}{3}\right)\cdot...\cdot\left(1-\dfrac{1}{10}\right)\left(1+\dfrac{1}{10}\right)\)
=>22/x=1/2*2/3*...*9/10*3/2*4/3*...*11/10
=>22/x=1/10*11/2=11/20=22/40
=>x=40
TA
18 tháng 12 2020
a) \(5x-65=5.3^2 \\ 5x-65=45\\5x=45+65\\5x=110\\x=22\)
b) \(200-(2x+6)=4^3\\2x+6=200-4^3\\2x+6=136\\2x=130\\x=65\)
c) \(2(x-51)=2.2^3+20\\2(x-51)=16+20\\2(x-51)=36\\x-51=18\\x=51+18=69\)
d) \(135-5(x+4)=35\\5(x+4)=135-45\\5(x-4)=90\\x-4=18\\x=18+4=22\)
e) \((2x-4)(15-3x)=0\\2(x-2).3(5-x)=0\\(x-2)(5-x)=0\\ \left[ \begin{array}{l}x-2=0\\5-x=0\end{array} \right. \\ \left[ \begin{array}{l}x=2\\x=5\end{array} \right.\)
f) \(2^{x+1} . 2^{2014}=2^{2016} \\ (2^{x+1} . 2^{2014}):2^{2014}=2^{2016} :2^{2014} \\ 2^{x=1}=2^{2016-2014} \\2^{x+1}=2^2\\x+1=2\\x=1\)
g) \(15+(x-1)^3=43\\(x-1)^3=15-42\\(x-1)^3=-27\\(x-1)^3=(-3)^3\\x-1=-3\\x=-2\)
h) \(15-x=17+(-9)\\15-x=17-9\\15-x=8\\x=15-8\\x=7\)
i) \(|x-5|=|-7|+|-4|\\|x-5|=7+4\\|x-5|=11\\ \left[ \begin{array}{l}x-5=11\\x-5=-11\end{array} \right. \\ \left[ \begin{array}{l}x=16\\x=-6\end{array} \right.\)
k) \(|x-3|-12=-9+|-7|\\|x-3|-12=-9+7\\|x-3|-12=-2\\|x-3|=10 \\ \left[ \begin{array}{l}x-3=10\\x-3=-10\end{array} \right. \\ \left[ \begin{array}{l}x=13\\x=-7\end{array} \right.\)
GN
GV Nguyễn Trần Thành Đạt
Giáo viên
11 tháng 8 2023
A.35 x 34 + 35 x 38 + 65 x 75 + 65 x 45
Câu này không tính hợp lí được
B. 12x 53 + 53 x 172 - 53 x 84
= 53 x (12 + 172 - 84)
= 53 x 100
= 5300
C. 36 x 28 + 36 x 82 + 64 x 69 + 64 x 41
= 36 x (28+82) + 64 x (69+41)
= 36 x 110 + 64 x 110
= (36+64) x 110
= 100 x 110
= 11 000
GN
GV Nguyễn Trần Thành Đạt
Giáo viên
11 tháng 8 2023
D. A = 1+2+3+...+100
= (1+ 100) x 50
= 101 x 50
= 5050
E. B =17+19+...+101+103
= (103 +17) x [(103 - 17):2 + 1]
= 120 x 44
=5280
G. D= 3x (12+13+14+15) + 3x(8+7+6+5)
= 3 x (5+6+7+8+12+13+14+15)
= 3 x (20 x 4)
= 3 x 80
=240
10 tháng 10 2019
Bài 1.
a, (x-2)-15=65
x-2=65+15
x-2=80
x=80+2
x=2
b, 115-2\(\times\)(x-3)=35
2\(\times\)(x-3)=115-35
2\(\times\)(x-3)=70
x-3=70:2
x-3=35
x=35+5
x=38
c, 35+2\(\times\)(x-3)=65
2\(\times\)(x-3)=65-35
2\(\times\)(x-3)=30
x-3=30:2
x-3=15
x=15+3
x=18
3\(\times\)(x-5)-16=11
3\(\times\)(x-5)=11+16
3\(\times\)(x-5)=27
x-5=27:3
x-5=9
x=9+5
x=14
Bài 2:
a, \(2^x-1=31\)
\(2^x=31-1\)
\(2^x=30\)
\(\Rightarrow\)Không có x thoả mãn điều kiện \(2^x=30\)
b, \(x^3-1=26\)
\(x^3=26+1\)
\(x^3=27\)
\(\Rightarrow x=3\) vì \(3^3=27\)
c, \(6^x-1+1=37\)
\(6^x-1=37-1\)
\(6^x-1=36\)
\(6^x=36+1\)
\(6^x=37\)
\(\Rightarrow\) Không có x thoả mãn điều kiện \(6^x=37\)
d, (x+2)\(^3\)-15\(^0\)=215
\(\left(x+2\right)^3-1=215\)
\(\left(x+2\right)^3=215+1\)
\(\left(x+2\right)^3=216\)
\(\left(x+2\right)^3=6^3\)
\(x+2=6\)
\(x=6-2\)
\(x=4\)
e, \(2\times\left(x-9\right)^2=2\)
\(\left(x-9\right)^2=2:2\)
\(\left(x-9\right)^2=1\)
\(\Rightarrow x-9=1\) vì \(1^2=1\)
x=1+9
x=10
g, \(3\times\left(x-5\right)^3=51\)
\(\left(x-5\right)^3=51:3\)
\(\left(x-5\right)^3=17\)
\(\Rightarrow\) Không có x thoả mãn điều kiện \(\left(x-5\right)^3=17\)
Nếu đúng thì tick cho mk nhé 
R
10 tháng 10 2019
Bài 1:
a)\(\left(x-2\right)-15=65\)
\(x-2=65+15\)
\(x-2=80\)
\(x=80+2\)
\(x=82\)
b)\(115-2\left(x-3\right)=35\)
\(2\left(x-3\right)=115-35\)
\(2\left(x-3\right)=80\)
\(x-3=80:2\)
\(x-3=40\)
\(x=40+3\)
c) \(35+2\left(x-3\right)=65\)
\(2\left(x-3\right)=65-35=30\)
\(x-3=30:2=15\)
\(x=15+3=18\)
d) \(3\left(x-5\right)-16=11\)
\(3\left(x-5\right)=11+16=27\)
\(x-5=27:3=9\)
\(x=9+5=14\)
Bài 2:
a) \(2^x-1=31\)
\(2^x=31+1=32\)
Vì \(2^5=32\Rightarrow x=5\)
b) \(x^3-1=26\)
\(x^3=26+1=27\)
Vì \(3^3=27\Rightarrow x=3\)
c)\(6^{x-1}+1=37\)
\(6^{x-1}=37-1=36\)
Vì \(6^6=36\Rightarrow x-1=6\Rightarrow x=6+1=7\)
d)\(\left(x+2\right)^3-15^0=215\)
\(\left(x+2\right)^3-1=215\)
\(\left(x+2\right)^3=215+1=216\)
Vì \(6^3=216\Rightarrow x+2=6\Rightarrow x=6-2=4\)
e)\(2\left(x-9\right)^2=2\)
\(\left(x-9\right)^2=2:2=1\)
Vì \(1^2=1\Rightarrow x-9=1\Rightarrow x=1+9=10\)
g) \(3\left(x-5\right)^3=51\)
\(\left(x-5\right)^3=51:3=17\)
VT
2
10 tháng 1 2016
A=1/3*5 + 1/5*7 + ....+ 1/99*101
A=1/2(2/3*5 + 2/5*7 + ...+ 2/99*101)
A=1/2[(1/3-1/5)+(1/5-1/7)+...+(1/99-1/101)]
A=1/2(1/3-1/101)
A=1/2 * 98/303
A=49/303
10 tháng 1 2016
\(A=\frac{1}{5}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}+...+\frac{1}{9999}\)
\(=\frac{1}{3X5}+\frac{1}{5X7}+\frac{1}{7X9}+\frac{1}{9X11}+...+\frac{1}{99X101}\)
\(2A=\frac{2}{3X5}+\frac{2}{5X7}+\frac{2}{7X9}+\frac{2}{9X11}+...+\frac{2}{99X101}\)
\(=\frac{5-3}{3X5}+\frac{7-5}{7X9}+\frac{9-7}{9X7}+\frac{11-9}{9X11}+...+\frac{101-99}{101}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{99}-\frac{1}{101}\)
\(=\frac{1}{3}-\frac{1}{101}=\frac{98}{303}\)
Từ đó ta suy ra:\(A=\frac{98}{303}:2=\frac{49}{303}\)
VT
1
19 tháng 1 2017
Bài 1:
a) \(24 - (-15) - 2\)
\(=39-2\)
\(=37\)
b) \((-85) + 10 - (-85) - 50\)
\(=[(-85)-(-85)]+10-50\)
\(=0+10-50\)
\(=10-50\)
\(=-40\)
c) \(71 - (-30) - (+18) + (-30)\)
\(=[(-30)-(-30)]+71-(+18)\)
\(=0+71-18\)
\(=71-18\)
\(=53\)
d) \(-(30) - (+37) + (+37) + (-85)\)
\(=[-(+37)+(+37)]-(30)+(-85)\)
\(=0-(30)+(-85)\)
\(=(-30)+(-85)\)
\(=-115\)
e) \((35-815) - (795-65)\)
\(=(-780)-730\)
\(=-1510\)
g) \((2002-79+15) + (-79+15)\)
\(=1938+(-64)\)
\(=1874\)
19 tháng 1 2017
Bài 2:
a) \(25 - (30+x) = x - (27-8)\)
\(25-30-x=x-27+8\)
\(x+x=25-30+27-8\)
\(2x=14\)
\(x=14\div2\)
\(x=7\)
b) \((x-12) - 15 = (20-17) - (18+x) \)
\(x-12-15=13-18-x\)
\(x-27=-5-x\)
\(x+x=-5+27\)
\(2x=22\)
\(x=22\div2\)
\(x=11\)
c) \(15 - x = 7 - (-2)\)
\(15-x=9\)
\(x=15-9\)
\(x=6\)
d) \(x - 35 = (-12) - 3\)
\(x-35=-15\)
\(x=-15+35\)
\(x=20\)
e) \(\left|5-x\right|-26=-15\)
\(\left|5-x\right|=-15+26\)
\(\left|5-x\right|=11\)
Từ đây ta có:
*Nếu \(5-x=11\)
\(x=5-11\)
\(x=-6\)
*Nếu \(5-x=-11\)
\(x=5-(-11)\)
\(x=16\)
Vậy \(x=-6;x=16\)