Tìm x :
a) -450 : [ -115 - 15 . ( 2x-1 )2 ] + 37 = 23 . 5
Tìm x :
a) -450 : [ -115 - 15 . ( 2x-1 )2 ] + 37 = 23 . 5
a: \(\Leftrightarrow-\dfrac{450}{-115-15\left(2x-1\right)^2}=8\cdot5-37=3\)
\(\Leftrightarrow\dfrac{450}{115+15\left(2x-1\right)^2}=3\)
\(\Leftrightarrow115+15\left(2x-1\right)^2=150\)
=>15(2x-1)2=35
=>(2x-1)2=7/3
hay \(x\in\left\{\dfrac{3+\sqrt{21}}{6};\dfrac{3-\sqrt{21}}{6}\right\}\)
Thực hiện phép tính ( tính nhanh nếu có thể)
a)3\(\dfrac{14}{19}\) +\(\dfrac{13}{17}\)+\(\dfrac{35}{43}\)+ 6\(\dfrac{5}{19}\) + \(\dfrac{8}{43}\)
b) \(\dfrac{-5}{7}\) . \(\dfrac{2}{11}\) + \(\dfrac{-5}{7}\) . \(\dfrac{9}{11}\) + 1\(\dfrac{5}{7}\)
c) 11\(\dfrac{3}{13}\) - ( 2\(\dfrac{4}{7}\) + 5\(\dfrac{3}{13}\))
d) \(\dfrac{2}{7}\) . 5\(\dfrac{1}{4}\) - \(\dfrac{2}{7}\) . 3\(\dfrac{1}{4}\)
a)
\(3\dfrac{14}{19}+\dfrac{13}{17}+\dfrac{35}{43}+6\dfrac{5}{19}+\dfrac{8}{43}\\ =\left(3\dfrac{14}{19}+6\dfrac{5}{19}\right)+\left(\dfrac{35}{43}+\dfrac{8}{43}\right)+\dfrac{13}{17}\\ =10+1+\dfrac{13}{17}\\ =11\dfrac{13}{17}\)
b)
\(\dfrac{-5}{7}\cdot\dfrac{2}{11}+\dfrac{-5}{7}\cdot\dfrac{9}{11}+1\dfrac{5}{7}\\ =\dfrac{-5}{7}\cdot\left(\dfrac{2}{11}+\dfrac{9}{11}\right)+1\dfrac{5}{7}\\ =\dfrac{-5}{7}\cdot1+1\dfrac{5}{7}\\ =\dfrac{-5}{7}+1\dfrac{5}{7}\\ =1\)
a) \(3\dfrac{14}{19}+\dfrac{13}{17}+\dfrac{35}{43}+6\dfrac{5}{19}+\dfrac{8}{43}\)
\(=\left(3\dfrac{14}{19}+6\dfrac{5}{19}\right)+\left(\dfrac{35}{43}+\dfrac{8}{43}\right)+\dfrac{13}{17}\)
\(=\left[\left(3+6\right)+\left(\dfrac{14}{19}+\dfrac{5}{19}\right)\right]+1+\dfrac{13}{17}\)
\(=\left[9+1\right]+1+\dfrac{13}{17}\)
\(=10+1+\dfrac{13}{17}\)
\(=11+\dfrac{13}{17}\)
\(=\dfrac{187}{17}+\dfrac{13}{17}\)
\(=\dfrac{200}{17}\)
b) \(\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{11}+1\dfrac{5}{7}\)
\(=\dfrac{-5}{7}.\left(\dfrac{2}{11}+\dfrac{9}{11}\right)+\dfrac{12}{7}\)
\(=\dfrac{-5}{7}.1+\dfrac{12}{7}\)
\(=\dfrac{-5}{7}+\dfrac{12}{7}\)
\(=\dfrac{7}{7}\)
\(=1\)
c) \(11\dfrac{3}{13}-\left(2\dfrac{4}{7}+5\dfrac{3}{13}\right)\)
= \(11\dfrac{3}{13}-2\dfrac{4}{7}-5\dfrac{3}{13}\)
\(=\left(11\dfrac{3}{13}-5\dfrac{3}{13}\right)-2\dfrac{4}{7}\)
\(=\left[\left(11-5\right)+\left(\dfrac{3}{13}-\dfrac{3}{13}\right)\right]-\dfrac{18}{7}\)
\(=\left[6+0\right]-\dfrac{18}{7}\)
\(=6-\dfrac{18}{7}\)
\(=\dfrac{42}{7}-\dfrac{18}{7}\)
\(=\dfrac{24}{7}\)
d) \(\dfrac{2}{7}.5\dfrac{1}{4}-\dfrac{2}{7}.3\dfrac{1}{4}\)
\(=\dfrac{2}{7}.\left(5\dfrac{1}{4}-3\dfrac{1}{4}\right)\)
\(=\dfrac{2}{7}.\left[\left(5-3\right)+\left(\dfrac{1}{4}-\dfrac{1}{4}\right)\right]\)
\(=\dfrac{2}{7}.\left[2+0\right]\)
\(=\dfrac{2}{7}.2\)
= \(\dfrac{4}{7}\)
viết phân số -64/120 dưới dạng tổng của 3 phân số có tử =-1 và mẫu khác nhau
Tìm x
\(\dfrac{1}{2}\)x + 150%x = 2014
\(\dfrac{1}{2}x+150\%x=2014\)
\(\Rightarrow\dfrac{1}{2}x+\dfrac{150}{100}x=2014\)
\(\Rightarrow\dfrac{1}{2}x+\dfrac{3}{2}x=2014\)
\(\Rightarrow x.\left(\dfrac{1}{2}+\dfrac{3}{2}\right)=2014\)
\(\Rightarrow2x=2014\)
\(\Rightarrow x=1007\)
thực hiện phép tính
M = 9 phần 40 - 11 phần 60 + 13 phần 84 - 15 phần 112
M= \(\dfrac{9}{40}-\dfrac{11}{60}+\dfrac{13}{84}-\dfrac{15}{112}\)
= (\(\dfrac{9}{40}-\dfrac{11}{60}\)) + (\(\dfrac{13}{84}-\dfrac{15}{112}\))
= (\(\dfrac{27}{120}-\dfrac{22}{120}\)) + (\(\dfrac{52}{336}-\dfrac{45}{336}\))
= \(\dfrac{1}{24}+\dfrac{1}{48}\)
= \(\dfrac{2}{48}+\dfrac{1}{48}\)
=\(\dfrac{3}{48}=\dfrac{1}{16}\)
E=1/3.5 +1/5.7 +....+1/2016.2018
giúp mình với hu hu hu
mình đang cần gấp
\(E=\dfrac{1}{3.5}+\dfrac{1}{5.7}+...+\dfrac{1}{2016.2018}\)
\(E=\dfrac{1}{2}.\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{2016}-\dfrac{1}{2018}\right)\)
\(E=\dfrac{1}{2}.\left(\dfrac{1}{3}-\dfrac{1}{2018}\right)\)
\(E=\dfrac{1}{2}.\dfrac{2015}{6054}\)
\(E=\dfrac{2015}{12108}\)
Cho số A = \(2017^{2018}+2018^{2017}\). Tìm số dư khi chia A cho 10 ?
Ta có:
20172 = 9 ( theo mod 10 ) ; 20178=(20172)4=94=1 ( theo mod 10 )
201710 = (20172)5 = 95=9 ( theo mod 10 )
2017100=( 201710)10=910=1 ( theo mod 10 )
20171000=( 2017100)10=110=1 ( theo mod 10 )
20172000=( 20171000)2=12= 1( theo mod 10 )
20172018=20172000.201710.20178=1.9.1=9( theo mod 10 )
2018=8 ( theo mod 10 ) ;20182=4 ( theo mod 10 )
20187=87=2 ( theo mod 10 )
201810=(20182)5=45=4 ( theo mod 10 )
2018100=(201810)10=410=6 ( theo mod 10 )
20181000= (2018100)10=610=6 ( theo mod 10 )
20182000=(20181000)2=62=6( theo mod 10 )
20182017=20182000.201810.20187=6.4.2=8
⇒ A = 20172018+20182017=9+8=7 ( theo mod 10 )
⇒ Số dư khi chia A = 20172018+20182017 cho 10 là 7
Ta có:
20172 = 9 ( theo mod 10 ) ; 20178=(20172)4=94=1 ( theo mod 10 )
201710 = (20172)5 = 95=9 ( theo mod 10 )
2017100=( 201710)10=910=1 ( theo mod 10 )
20171000=( 2017100)10=110=1 ( theo mod 10 )
20172000=( 20171000)2=12= 1( theo mod 10 )
20172018=20172000.201710.20178=1.9.1=9( theo mod 10 )
2018=8 ( theo mod 10 ) ;20182=4 ( theo mod 10 )
20187=87=2 ( theo mod 10 )
201810=(20182)5=45=4 ( theo mod 10 )
2018100=(201810)10=410=6 ( theo mod 10 )
20181000= (2018100)10=610=6 ( theo mod 10 )
20182000=(20181000)2=62=6( theo mod 10 )
20182017=20182000.201810.20187=6.4.2=8
⇒ A = 20172018+20182017=9+8=7 ( theo mod 10 )
⇒ Số dư khi chia A = 20172018+20182017 cho 10 là 7
bài 1 : tìm x, biết:
A) X/3 - 1/2 = 1/5 B) x/5 + 1/2 = 6/10 c) x +3 /15 = 1/3 d) x -14/4 =1/4
đ) 1/2 x + 1/2 =5/2 n) -2/3 1/3 ( 2x -5 )=3/2 i) ( 3x -1) ( -1/2 x +5 ) =0 j) x-2/4 = 5+x/3
q) 3/x + 5 = 15% p) | x - 1/3 =5/6 m) 2| 1/2 x - 1/3 | - 3/2 = 1/4
z) ( 4,5 - 2 x) . ( -11/7) = 11/14 y) ( x/7 + 0,25 ) = -1/28
giup minh nhé
mai nộp rồi
cam ơn bạn rất nhiều
tick cho bạn nào đầu tiên
a) x/3 - 1/2 = 1/5
<=> x/3 = 1/5 + 1/2
<=> x/3 = 7/10
<=> 10x = 3 . 7
<=> 10x = 21
<=> x = 21 : 10
<=> x = 2,1
Vậy x = 2,1
b) x/5 + 1/2 = 6/10
<=> x/5 = 6/10 - 1/2
<=> x/5 = 6/10 - 5/10
<=> x/5 = 1/10
<=> 10x = 5
<=> x = 5 : 10
<=> x = 0,5
Vậy x = 0,5
c) x + 3/15 = 1/3
<=> x = 1/3 - 3/15
<=> x = 5/15 - 3/15
<=> x = 2/15
Vậy x = 2/15
d) x - 14/4 = 1/4
<=> x = 1/4 + 14/4
<=> x = 15/4
Vậy x = 15/4
tính H = \(\dfrac{\dfrac{1}{99}+\dfrac{2}{98}+\dfrac{3}{97}+...+\dfrac{98}{2}+\dfrac{99}{1}}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{100}}:\dfrac{92-\dfrac{1}{9}-\dfrac{2}{10}-\dfrac{3}{11}-...-\dfrac{92}{100}}{\dfrac{1}{45}+\dfrac{1}{50}+\dfrac{1}{55}+...+\dfrac{1}{500}}\)
bài 160-toán tập 2-sgk
Đề bài: Tìm phân số a/b bằng phân số 18/27 biết rằng ƯCLN (a, b) = 13.
Giải
Ta có: \(\dfrac{a}{b}=\dfrac{18}{27}=\dfrac{2}{3}\) và (a,b)=13 nên phân số a/b đã được rút gọn 13 lần, hay phân số cần tìm bằng: \(\dfrac{a}{b}=\dfrac{2\cdot13}{3\cdot13}=\dfrac{26}{39}\)