1, Tính nhanh tính hợp lí (nếu có thể)
\(\dfrac{3}{7}+\dfrac{4}{7}\div\dfrac{4}{14}+2,5-75\%=?\)
Khó quá các bn à!!!!
1) tính hợp lí ( nếu có thể )
c) \(\dfrac{2}{-11}\). 6\(\dfrac{2}{7}\)+ \(\dfrac{3}{7}\):3 + 5 d) 1,75 : 5 + 2,5 . ( \(4^2\)- 4. 4,1)
2) tìm x
a) 1/2-x=-1/6 b) x+3,5=7,8-12,6:2 c) 7/35 = 35-x/-105
2:
a: =>x=1/2+1/6=3/6+1/6=4/6=2/3
b: =>x+3,5=7,8-6,3=1,5
=>x=1,5-3,5=-2
c: =>(35-x)/-105=1/5
=>35-x=-21
=>x=56
1
c hình như tính bình thường thôi:v
d
= 1,75 : 5 + 2,5 . (16 – 4 . 4,1)
= 1,75 : 5 + 2,5 . (16 – 16,4)
= 1,75 : 5 + 2,5 . (−0,4)
= 0,35 − 1
= −0,65.
2
a
\(\Rightarrow x=\dfrac{1}{2}+\dfrac{1}{6}=\dfrac{3}{6}+\dfrac{1}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)
b
\(\Rightarrow x+\dfrac{35}{10}=\dfrac{78}{10}-\dfrac{63}{5}:2\\ \Rightarrow x+\dfrac{35}{10}=\dfrac{78}{10}-\dfrac{63}{10}=\dfrac{15}{10}\\ \Rightarrow x=\dfrac{15}{10}-\dfrac{35}{10}=-2\)
c không rõ đề:v
\(1,\dfrac{2}{-11}.6\dfrac{2}{7}+\dfrac{3}{7}:3+5\\ =\dfrac{2}{-11}.\dfrac{44}{7}+\dfrac{3}{7}\times\dfrac{1}{3}+5\\ =-\dfrac{88}{77}+\dfrac{3}{21}+5\\ =-\dfrac{8}{7}+\dfrac{1}{7}+5\\ =-1+5\\ =4\)
\(d,1,75:5+2,5.\left(4^2-4.4,1\right)\\ =0,35+2,5.\left(16-16,4\right)\\ =0,35+2,5.0,4\\ =0,35+1\\ =1,35\)
`2,`
`a, 1/2 -x=-1/6`
`=> x= 1/2 -(-1/6)`
`=> x= 1/2 +1/6`
`=> x= 3/6+1/6`
`=>x= 4/6`
`=>x=2/3`
Vậy `x=2/3`
`b, x+3,5 =7,8 -12,6 :2`
`=> x+3,5 = 7,8 - 6,3`
`=> x+3,5=1,5`
`=> x= 1,5-3,5`
`=>x=-2`
Vậy `x=-2`
\(c,\dfrac{7}{35}=\dfrac{35-x}{-105}\\ \Rightarrow7.\left(-105\right)=35.\left(35-x\right)\\ \Rightarrow-735=1225-35x\\ \Rightarrow-735-1225=-35x\\ \Rightarrow-1960=-35x\\ \Rightarrow x=-1960:\left(-35\right)\\ \Rightarrow x=56\)
Vậy `x=56`
Thực hiện phép tính( tính hợp lý nếu có thể)
- \(\dfrac{3}{4}\) - ( \(\dfrac{7}{14}\) + \(\dfrac{3}{4}\) ) + \(\dfrac{5}{8}\)
\(=\dfrac{-3}{4}-\dfrac{1}{2}-\dfrac{3}{4}+\dfrac{5}{8}=\dfrac{-6}{4}+\dfrac{5}{8}-\dfrac{1}{2}=-2+\dfrac{5}{8}=\dfrac{-16+5}{8}=-\dfrac{11}{8}\)
Thực hiện phép tính (hợp lí nếu có thể):
a) (\(\dfrac{-6}{11}\)) . \(\dfrac{7}{10}\) . \(\dfrac{11}{-6}\) . (-20)
b) (\(-1\dfrac{1}{2}\)) : \(\dfrac{3}{4}\) . \(-4\dfrac{1}{2}\))
c) \(13\dfrac{2}{7}\) : (\(\dfrac{-8}{9}\)) + \(2\dfrac{5}{7}\) : (\(\dfrac{-8}{9}\))
\(a.\left[-\dfrac{6}{11}.\dfrac{11}{-6}\right].\dfrac{7}{10}.\left(-20\right)=1.7.\left(-2\right)=-14\)
\(b.\dfrac{-1}{2}:\dfrac{3}{4}.\dfrac{-7}{2}=\dfrac{7}{4}:\dfrac{3}{4}=\dfrac{7}{3}\)
\(c.\dfrac{93}{7}:-\dfrac{8}{9}+\dfrac{19}{7}:\dfrac{-8}{9}=\left(\dfrac{93}{7}+\dfrac{19}{7}\right):-\dfrac{8}{9}=\dfrac{-9}{8}.\dfrac{112}{7}=-18\)
Tính nhanh (nếu có thể):
a) \(5\dfrac{5}{27}+\dfrac{7}{23}+0,5.\dfrac{5}{27}+\dfrac{16}{23}\)
b) \(\dfrac{10^9.49^4}{14^8.25^5}\)
các bn ghi rõ cách giải giùm mình đcc ko, mình cảm ơn
a) https://hoc247.net/hoi-dap/toan-7/thuc-hien-phep-tinh-5-5-27-7-23-0-5-5-27-16-23-faq218258.html
b) https://hoidap247.com/cau-hoi/1507941
b) \(\dfrac{10^9.49^4}{14^8.25^5}=\dfrac{\left(2.5\right)^9.\left(7^2\right)^4}{\left(7.2\right)^8.\left(5^2\right)^5}=\dfrac{2^9.5^9.7^6}{7^8.2^8.5^{10}}=\dfrac{2}{7.7.5}=\dfrac{2}{245}\)
\(a,=\left(\dfrac{140}{27}+\dfrac{1}{2}\cdot\dfrac{5}{27}\right)+\left(\dfrac{7}{23}+\dfrac{16}{23}\right)\\ =\left(\dfrac{140}{27}+\dfrac{5}{54}\right)+1=\dfrac{285}{54}+1=\dfrac{339}{54}=\dfrac{113}{18}\\ b,=\dfrac{2^9\cdot5^9\cdot7^8}{7^8\cdot2^8\cdot5^{10}}=\dfrac{2}{5}\)
Thực hiện phép tính (hợp lí nếu có thể):
a) \(13\dfrac{2}{7}\) : (\(\dfrac{-8}{9}\)) + \(2\dfrac{5}{7}\) : (\(\dfrac{-8}{9}\))
b) (\(\dfrac{-6}{11}\)) . \(\dfrac{7}{10}\) . (\(\dfrac{11}{-6}\)) . (-20)
c) (\(-1\dfrac{1}{2}\)) : \(\dfrac{3}{4}\) . (\(-4\dfrac{1}{2}\))
a) \(=\left(13\dfrac{2}{7}+2\dfrac{5}{7}\right):\left(-\dfrac{8}{9}\right)\)
\(=16:\dfrac{-8}{9}=\dfrac{-8\cdot\left(-2\right)\cdot9}{-8}=-18\)
b)
\(=\left(\dfrac{-6}{11}\cdot\dfrac{11}{-6}\right)\cdot\dfrac{7\cdot10\cdot\left(-2\right)}{10}\)
\(=-14\)
c) \(=\dfrac{-1}{2}\cdot\dfrac{4}{3}\cdot\dfrac{-7}{2}\)
\(=\dfrac{-1\cdot2\cdot2\cdot\left(-7\right)}{2\cdot3\cdot2}=\dfrac{7}{3}\)
Tính (Tính hợp lí nếu có thể)
a) \(\dfrac{-7}{12}\)-\(\dfrac{3}{36}\)
b) (4-\(\dfrac{5}{12}\)):2+\(\dfrac{5}{24}\)
c) \(\dfrac{8}{9}\)+\(\dfrac{1}{9}\).\(\dfrac{2}{13}\)+\(\dfrac{1}{9}\).\(\dfrac{11}{13}\)
d) \(\dfrac{3}{4}\).\(\dfrac{8}{9}\).\(\dfrac{15}{16}\). ... .\(\dfrac{9999}{10000}\)
e) \(\dfrac{3}{1.4}\)+\(\dfrac{3}{4.7}\)+\(\dfrac{3}{7.10}\)+...+\(\dfrac{3}{97.100}\)
*Lưu ý: Mong các anh chị trình bày chi tiết để em có thể hiểu bài, em xin các anh chị đừng viết mỗi kết quả xong em chả biết một cái gì ;-;
a: =-21/36-3/36=-24/36=-2/3
b: =43/12*1/2+5/24=43/24+5/24=2
c: =8/9+1/9=1
e: =1-1/4+1/4-1/7+...+1/97-1/100
=1-1/100=99/100
\(\text{Thực hiện phép tính một cách hợp lý nhất (nếu có thể):}\)
\(1\)) \(\left(\dfrac{-8}{13}:\dfrac{3}{7}+\dfrac{-5}{13}:\dfrac{3}{7}\right).\dfrac{\left(-4\right)^3.\left|-3\right|}{7}\)
\(2\)) \(75\)\(\text{%}\)\(-\left(\dfrac{5}{2}+\dfrac{5}{3}\right)+\left(-\dfrac{1}{2}\right)^2\)
Giải:
1) (-8/13:3/7+-5/13:3/7).(-4)3.|-3|/7
=[7/3.(-8/13+-5/13)].-192/7
=[7/3.(-1)].-192/7
=-7/3.-192/7
=64
2) 75%-(5/2+5/3)+(-1/2)2
=3/4-25/6+1/4
=(3/4+1/4)-25/6
=1-25/6
=-19/6
Chúc bạn học tốt!
1) \(\left(\dfrac{-8}{13}:\dfrac{3}{7}+\dfrac{-5}{13}:\dfrac{3}{7}\right).\dfrac{\left(-4\right).|-3|}{7}\)
= \(\left[\left(\dfrac{-8}{13}+\dfrac{-5}{13}\right):\dfrac{3}{7}\right].\dfrac{-64.3}{7}\)
= \(\left[-1:\dfrac{3}{7}\right].\dfrac{-192}{7}\)
= \(\dfrac{-7}{3}.\dfrac{-192}{7}\)
= \(64\)
2) \(75\%-\left(\dfrac{5}{2}+\dfrac{5}{3}\right)+\left(-\dfrac{1}{2}\right)^2\)
= \(\dfrac{3}{4}-\dfrac{25}{6}+\dfrac{1}{4}\)
= \(\left(\dfrac{3}{4}+\dfrac{1}{4}\right)-\dfrac{25}{6}\)
= \(1-\dfrac{25}{6}\)
= \(\dfrac{-19}{6}\)
Chúc bạn học tốt !
Tính hợp lí nếu có thể:
\(\dfrac{3}{4}\).\(\dfrac{8}{9}\).\(\dfrac{15}{16}\). ... .\(\dfrac{9999}{10000}\)
Mong các anh chị trình bày chi tiết
Bài này cũng ko phải toán khó đâu ạ ;-;
= 3/4 . 8/9 . 15/16 . ... . 9999/10000
= 3 . 8 . 15 . ... . 9999/ 4 . 9 . 16 . ... . 10000
= (1 . 3) . (2 . 4) . (3 x 5) . ... . (99 . 101)/ (2 . 2) . (3 . 3) . (4 x 4) . ... . (100 . 100)
= (1 . 2 . 3 . ... . 99) . (3 . 4 . 5 . ... . 101)/ (2 . 3 . 4 . ... . 100) . (2 . 3 . 4 . ... . 100)
= 1. 101/ 100 . 2
= 101/200
\(\dfrac{3}{4}.\dfrac{8}{9}.\dfrac{15}{16}...\dfrac{9999}{10000}.\\ =\dfrac{1.3}{2^2}.\dfrac{2.4}{3^2}.\dfrac{3.5}{4^2}...\dfrac{99.101}{100^2}.\\ =\dfrac{1.3.2.4.3.5...99.101}{2^2.3^2.4^2...100^2}.\\ =\dfrac{\left(1.2.3...99\right).\left(3.4.5...101\right)}{\left(2.3.4...100\right).\left(2.3.4...100\right)}.\\ =\dfrac{\left(1.1.1...1\right).\left(1.1.1...101\right)}{\left(1.1.1...100\right).\left(2.1.1...1\right)}=\dfrac{1.101}{100.2}=\dfrac{101}{200}.\)
Thực hiện phép tính (tính nhanh nếu có thể)
c) \(5\dfrac{2}{5}\)✖\(4\dfrac{2}{7}\)+\(5\dfrac{5}{7}\)✖\(5\dfrac{2}{5}\)
d) 75%-\(1\dfrac{1}{2}\)+0,5:\(\dfrac{5}{12}\)-\(\left(\dfrac{-1}{2}\right)^2\)