x+1/17 + x+2/16 = x+4/7
x+1/17 + x+2/16 = x+4/7
\(\dfrac{x+1}{17}+\dfrac{x+16}{2}=\dfrac{x+4}{7}\)
\(\Rightarrow\dfrac{x+1}{17}+1+\dfrac{x+2}{16}+1=\dfrac{x+4}{7}+2\)
\(\Rightarrow\dfrac{x+18}{17}+\dfrac{x+18}{16}-\dfrac{x+18}{7}=0\)
\(\Leftrightarrow\left(x+18\right)\left(\dfrac{1}{17}+\dfrac{1}{16}-\dfrac{1}{7}\right)=0\)
mà \(\dfrac{1}{17}+\dfrac{1}{16}-\dfrac{1}{4}\ne0\)
\(\Rightarrow x+18=0\Rightarrow x=-18\)
Vậy ....
1 x 2 x 3 x 4 x 5 x 6 x 7 x ( 4 x 8 - 16 x 2 ) x 15 x 16 x 17 ... x 2019 x 2020
Tính ngoặc tròn
\(4\cdot8-16\cdot2\)
\(=32-32\)
\(=0\)
Vậy tích trên bằng 0 ( vì có 1 thừa số = 0 )
Bài giải
1 x 2 x 3 x 4 x 5 x 6 x 7 x ( 4 x 8 - 16 x 2 ) x 15 x 16 x 17 ... x 2019 x 2020
= 1 x 2 x 3 x 4 x 5 x 6 x 7 x ( 32 - 32 ) x 15 x 16 x 17 ... x 2019 x 2020
= 1 x 2 x 3 x 4 x 5 x 6 x 7 x 0 x 15 x 16 x 17 ... x 2019 x 2020
= 0
chắt do tui quên tính 4 x 8 - 16 x 2 nên mới vậy :v
Tìm x biết x-2/x-1=x+4/x+7
x-18/x+4=x-17/x+16
Tìm số nguyên x, biết:
1) -16 + 23 + x = - 16
2) 2x – 35 = 15
3) 3x + 17 = 12
4) (2x – 5) + 17 = 6
5) 10 – 2(4 – 3x) = -4
6) - 12 + 3(-x + 7) = -18
Tìm số nguyên x, biết:
1) -16 + 23 + x = - 16
7+x=-16
x=-16-7
x=-23
2) 2x – 35 = 15
2x=15+35
2x=50
x=50:2
x=25
3) 3x + 17 = 12
3x=12-17
3x=-5
x=-5/3
4) (2x – 5) + 17 = 6
2x-5=6-17
2x-5=-11
2x=-11+5
2x=-6
x=-6:2
x=-3
5) 10 – 2(4 – 3x) = -4
2(4-3x)=10-(-4)
2(4-3x)=14
4-3x=14:2
4-3x=7
3x=4-7
3x=-3
x=-3:3
x=-1
6) - 12 + 3(-x + 7) = -18
3(-x+7)=-18-(-12)
3(x+7)=-6
x+7=-6:3
x+7=-2
x=-2-7
x=-9
tự đi mà làm
1/ (\(\left(-\dfrac{2}{3}\right)\)\(^2\) x \(\dfrac{-9}{8}\) - 25% x \(\dfrac{-16}{5}\)
2/ -1\(\dfrac{2}{5}\) x 75% + \(\dfrac{-7}{5}\) x 25%
3/ -2\(\dfrac{3}{7}\) x (-125%) + \(\dfrac{-17}{7}\) x 25%
4/ (-2)\(^3\) x (\(\dfrac{3}{4}\) x 0.25) : (2\(\dfrac{1}{4}\) - 1\(\dfrac{1}{6}\))
1) Ta có: \(\left(-\dfrac{2}{3}\right)^2\cdot\dfrac{-9}{8}-25\%\cdot\dfrac{-16}{5}\)
\(=\dfrac{4}{9}\cdot\dfrac{-9}{8}-\dfrac{1}{4}\cdot\dfrac{-16}{5}\)
\(=\dfrac{-1}{2}+\dfrac{4}{5}\)
\(=\dfrac{-5}{10}+\dfrac{8}{10}=\dfrac{3}{10}\)
2) Ta có: \(-1\dfrac{2}{5}\cdot75\%+\dfrac{-7}{5}\cdot25\%\)
\(=\dfrac{-7}{5}\cdot\dfrac{3}{4}+\dfrac{-7}{5}\cdot\dfrac{1}{4}\)
\(=\dfrac{-7}{5}\left(\dfrac{3}{4}+\dfrac{1}{4}\right)=-\dfrac{7}{5}\)
3) Ta có: \(-2\dfrac{3}{7}\cdot\left(-125\%\right)+\dfrac{-17}{7}\cdot25\%\)
\(=\dfrac{-17}{7}\cdot\dfrac{-5}{4}+\dfrac{-17}{7}\cdot\dfrac{1}{4}\)
\(=\dfrac{-17}{7}\cdot\left(\dfrac{-5}{4}+\dfrac{1}{4}\right)\)
\(=\dfrac{17}{7}\)
4) Ta có: \(\left(-2\right)^3\cdot\left(\dfrac{3}{4}\cdot0.25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)
\(=\left(-8\right)\cdot\left(\dfrac{3}{4}\cdot\dfrac{1}{4}\right):\left(\dfrac{9}{4}-\dfrac{7}{6}\right)\)
\(=\left(-8\right)\cdot\dfrac{3}{16}:\dfrac{54-28}{24}\)
\(=\dfrac{-3}{2}\cdot\dfrac{24}{26}\)
\(=\dfrac{-72}{52}=\dfrac{-18}{13}\)
Tìm x thuộc Z, biết
a, -5/7 + 1 + 30/-7 <_ x <_ -1/6 + 1/3 + 5/6
b, 1/2 - ( 1/3 + 1/4 ) < x < 1/48 - ( 1/16 - 1/6 )
c, ( x - 1/2 ) × ( x +3/4 ) < 0
d, 3/ ( x +2) ×( x +5) + 5/ ( x +5 ) × ( x+ 10) + 7/ ( x +10) ( x +17) = x / ( x+2) × ( x + 17)
a, -5/7+ 1+ 30/-7< x < -1/6+ 1/3 +5/6
<=> -4< x <1
<=> x = -3; -2; -1; 0
a, \(\dfrac{-5}{7}+1+\dfrac{30}{-7}\le x\le\dfrac{-1}{6}+\dfrac{1}{3}+\dfrac{5}{6}\)
<=> -4 \(\le x\le1\)
Do x \(\in Z\Rightarrow x=-4;-3;-2;-1;0;1\)
b, \(\dfrac{1}{2}-\left(\dfrac{1}{3}+\dfrac{1}{4}\right)< x< \dfrac{1}{48}-\left(\dfrac{1}{16}-\dfrac{1}{6}\right)\)
<=> -\(\dfrac{1}{12}< x< \dfrac{1}{8}\)
Do x \(\in Z\Rightarrow x=0;1\)
@Mai Tran
c, Do (x - \(\dfrac{1}{2}\))(x + \(\dfrac{3}{4}\)) < 0
=> x - \(\dfrac{1}{2};x+\dfrac{3}{4}\) khác dấu
Có x - \(\dfrac{1}{2}< x+\dfrac{3}{4}\Rightarrow x-\dfrac{1}{2}< 0;x+\dfrac{3}{4}>0\)
=> \(\left[{}\begin{matrix}x-\dfrac{1}{2}< 0\\x+\dfrac{3}{4}>0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x< \dfrac{1}{2}\\x>-\dfrac{3}{4}\end{matrix}\right.\)<=> -\(\dfrac{3}{4}< x< \dfrac{1}{2}\)
Do x \(\in Z\Rightarrow x=0\)
@Mai Tran
Tính nhanh
A)(17/4 x 12/7 - 2/7 x 17/4 - 3/7 x 17/4) x 6/51
B)45 x 16 - 17/ 45 x 15 + 28
a(17/4x12/7-2/7x17/4-3/7x17/4)x6/51
=[17/4x(12/7-2/7-3/7)]x6/51
=17/4x1x6/51
=17/4x6/51
=102/204=1/2
b,45x16-17/45x15+28
=15x3x16-17/45x15+28
=15x48-17/45x15+28
=15x2160/45-17/45x15+28
=15x(2160/45-17/45)+28
=15x2143/45+28
=2143/3+84/3
=2227/3
tính nhanh à,lên google search í
(Người THÀNH CÔNG luôn có một lối đi riêng)
x^2 -13/4 - x^2 -15/6=x^2-16/7- x^2-17/8
a.,\(\dfrac{4}{5}+5\dfrac{1}{2}\text{x }\left(4,5-2\right)=\dfrac{7}{10}\) b,125%x\(\dfrac{17}{4}:\left(1\dfrac{5}{16}-0,5\right)+2008\)
c,\(\dfrac{5}{11}+\left(\dfrac{16}{11}+1\right)\) d, \(\dfrac{3}{17}+\dfrac{11}{4}+\dfrac{5}{8}+\dfrac{14}{17}+\dfrac{3}{8}\)
`a)4/5+5 1/2 xx (4,5-2)+7/10`
`=4/5+11/2*2,5+7/10`
`=0,8+2,2+0,7`
`=3+0,7=3,7`
`b)125%xx 17/4:(1 5/16-0,5)+2008`
`=1,25xx4,25:13/16+2008`
`=85/13+2008`
`=2014 7/13`
`c)5/11+(16/11+1)`
`=5/11+1+5/11+1`
`=2+10/11=32/11`
`d)3/17+11/4+5/8+14/17+3/8`
`=3/17+14/17+5/8+3/8+11/4`
`=1+1+11/4`
`=19/4`
a)
\(\dfrac{4}{5}+5\dfrac{1}{2}x\left(4,5-2\right)=\dfrac{7}{10}\)
<=> \(\dfrac{11}{2}x\times2,5=\dfrac{7}{10}-\dfrac{4}{5}=\dfrac{-1}{10}\)
<=> \(\dfrac{55}{4}x=\dfrac{-1}{10}< =>x=\dfrac{-2}{275}\)
b) \(125\%\times\dfrac{17}{4}:\left(1\dfrac{5}{16}-0,5\right)+2008\)
= \(\dfrac{85}{16}:\left(\dfrac{21}{16}-\dfrac{1}{2}\right)+2008=\dfrac{85}{16}:\dfrac{13}{16}+2008=\dfrac{26189}{13}\)
c) \(\dfrac{5}{11}+\left(\dfrac{16}{11}+1\right)\)
= \(\dfrac{21}{11}+1=\dfrac{32}{11}\)
d) \(\left(\dfrac{3}{17}+\dfrac{14}{17}\right)+\left(\dfrac{5}{8}+\dfrac{3}{8}\right)+\dfrac{11}{4}\)
= 1 + 1 + \(\dfrac{11}{4}\) = \(\dfrac{19}{4}\)