Chứng tỏ: 1<1\5+1\6+...+1\16+1\17<2
Thực hiện phép tính
1) 6/7 + 5/8 : 5 - 3/16 . ( -2)mũ 2
2) -1/6 + 2/3 . -3/4 + (-2)mũ 2 / 5 chú ý : / là phần nha
3) 2 3/4 . (-0,4 ) + 1 3/5 . 1,75 + (-7,2 ) : 9/11
4) 1/8 . 15 2/5 + 1 4/5 . 7/8 - 17 1/5 . 1/8
Thực hiện phép tính
1) 6/7 + 5/8 : 5 - 3/16 . ( -2)mũ 2
2) -1/6 + 2/3 . -3/4 + (-2)mũ 2 / 5 chú ý : / là phần nha
3) 2 3/4 . (-0,4 ) + 1 3/5 . 1,75 + (-7,2 ) : 9/11 lẹ nha mình đang cần gấp mai mình phải nộp
4) 1/8 . 15 2/5 + 1 4/5 . 7/8 - 17 1/5 . 1/8
Bài 1: Tìm x , biết:
1) x - 2 = -6 12) 3 . | x - 1 | - 5 = 7
2) -5 . x - ( -3 ) = 13 13) -12 . ( x - 5 ) + 7 . ( 3 - x ) = 5
3) 15 - ( x - 7 ) = -21 14) ( x - 2 ) . ( x + 4 ) = 0
4) 3 .x + 17 = 2 15) ( x - 2 ) . ( x + 15 ) = 0
5) 45 - ( x - 9 ) = -35 16) ( 7 - x ) . ( x + 19 ) = 0
6) ( -5 ) + x = 15 17) -5 < x < 1
7) 2 . x - ( -17 ) = 15 18) | x | < 3
8) | x - 2 | = 3 19) ( x - 3 ) . ( x - 5 ) < 0
9) | x - 3 | - 7 = 13 20) 2 . x2 - 3 = 29
10) 72 - 3 . | x + 1 | = 9 21) -6 . x - ( -7) = 25
11) 17 - ( 43 - | x | ) = 45 22) 46 =- ( x - 11 ) = -48
a) ( 1/3 - 1/4 ) + ( 1/4 - 1/5 ) +
( 1/5 - 1/6 ) + ( 1/6 - 1/7 ) + ( 1/7 - 1/8 )
b) 10/17 - 5/13 - -7/17 - 8/13
Giúp ạ!
a)\(\dfrac{2}{7}+\dfrac{-3}{8}+\dfrac{11}{7}+\dfrac{1}{7}_{ }+\dfrac{5}{-8}\)
b)\(\dfrac{3}{17}+\dfrac{-5}{13}+\dfrac{-18}{35}+\dfrac{14}{17}+\dfrac{17}{-35}_{ }+\dfrac{-8}{13}\)
c)\(\dfrac{-3}{8}+\dfrac{12}{25}+\dfrac{5}{-8}+\dfrac{2}{-5}+\dfrac{13}{25}\)
d)\(\dfrac{-5}{21}+\left(\dfrac{-16}{21}+1\right)\)
e)\(\dfrac{-3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)\)
f)\(\left(\dfrac{-1}{6}+\dfrac{5}{-12}\right)+\dfrac{7}{12}\)
Bài 1 : Tính bằng cách hợp lí :
a ) A = \((\) \(\dfrac{\dfrac{1}{13}-\dfrac{1}{17}-\dfrac{1}{23}}{\dfrac{2}{13}-\dfrac{2}{17}-\dfrac{2}{23}}\) \()\) . \((\) \(\dfrac{\dfrac{1}{3}-0,25+0,2}{1\dfrac{1}{6}-0,875+0,7}\) \()\) + \(\dfrac{6}{7}\)
b ) B = 2000 : \([\) \((\) \(\dfrac{0,4-\dfrac{2}{9}+\dfrac{2}{11}}{1,4-\dfrac{7}{9}+\dfrac{7}{11}}\) \()\) . \((\) \(\dfrac{-1\dfrac{1}{6}+0,875-0,7}{\dfrac{1}{3}-0,25+\dfrac{1}{5}}\) \()\) \(]\)
c ) C = 10101 . \((\) \(\dfrac{5}{111111}+\dfrac{2}{222222}-\dfrac{4}{21.143.37}\) \()\)
Bài 2 : Tìm x :
a ) \(\dfrac{1}{2.5}+\dfrac{1}{5.8}+\dfrac{1}{8.11}+......+\dfrac{1}{125.155}-x=\dfrac{1}{310}\)
b ) \(1\dfrac{3}{5}+(\dfrac{\dfrac{2}{7}\dfrac{2}{17}\dfrac{2}{37}}{\dfrac{5}{7}\dfrac{5}{17}\dfrac{5}{37}}).\) x = \(\dfrac{16}{5}\)
Bài 3: Thực hiện phép tính một cách hợp lý:
m) \(\left(\frac{-5}{12}+\frac{6}{11}\right)+\left(\frac{7}{17}+\frac{5}{11}+\frac{5}{12}\right)\) n) \(\left(\frac{9}{16}+\frac{8}{-27}\right)+\left(1+\frac{7}{16}+\frac{-19}{27}\right)\) o) \(\left(6-2\frac{4}{5}\right).3\frac{1}{8}-1\frac{3}{5}:\frac{1}{4}\)
gọi A =n ^2+n+1(nEN). chung to A ko chia het cho 2.chung to A ko chia het cho 5
