\(\left[516-\left(25\cdot4+16\right)\right]:8-68\)

\(=\dfrac{\left[516-100-16\right]}{8}-68\)

\(=\dfrac{400}{8}-68=50-68=-18\)

13500 = 135 ×100

257 > 8762 ×0

26 ×11 > 280

320 : 16×2=320:16:2

1600 : 10 < 1006

15 ×8×37=37×15×8

13500 = 135 ×100

257 > 8762 ×0

26 ×11 > 280

320 : 16×2=320:16:2

1600 : 10 < 1006

15 ×8×37=37×15×8

a: \(\dfrac{-3}{25}\cdot\dfrac{4}{17}\cdot\dfrac{5}{-3}\cdot\dfrac{17}{2}=\dfrac{4}{17}\cdot\dfrac{17}{2}\cdot\dfrac{3}{25}\cdot\dfrac{5}{3}=2\cdot\dfrac{1}{5}=\dfrac{2}{5}\)

b: \(=-\dfrac{8}{15}\cdot\dfrac{13}{16}\cdot\dfrac{30}{13}=\dfrac{-8}{15}\cdot\dfrac{15}{8}=-1\)

c: \(=\dfrac{3}{11}\left(\dfrac{2}{9}\cdot\dfrac{-8}{33}+\dfrac{7}{9}\right)=\dfrac{3}{11}\cdot\dfrac{215}{297}=\dfrac{2015}{1089}\)

a) \(18+25\times4-4^3\)

\(=18+100-64\)

\(=118-64\)

\(=54\)

b) \(275-\left(49+125\div5^3\right)\)

\(=275-\left(49+125\div125\right)\)

\(=275-\left(49+1\right)\)

\(=275-49-1\)

\(=226-1\)

\(=225\)

c) \(2015+\left(8\times15-\left(18-8\right)^2\right)\)

\(=2015+\left(8\times15-\left(10\right)^2\right)\)

\(=2015+\left(8\times15-100\right)\)

\(=2015+\left(120-100\right)\)

\(=2015+20\)

\(=2035\)

Đặt tổng trên = A

\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{152}\)

\(Ax2=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{76}\)

\(Ax2-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{76}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{152}\right)\)

\(A=1-\frac{1}{152}\)

\(A=\frac{151}{152}\)

\(\text{Đặt tổng trên = A}\)

\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{152}\)

\(Ax2=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{76}\)

\(Ax2-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{76}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{16}+...+\frac{1}{152}\right)\)

\(A=1-\frac{1}{152}\)

$A=\frac{151}{152}$

2, 

a) \(315-\left(135-x\right)=215\)

\(\Rightarrow135-x=315-215\)

\(\Rightarrow135-x=100\)

\(\Rightarrow x=135-100\)

\(\Rightarrow x=35\)

b) \(x-320:32=25\cdot16\)

\(\Rightarrow x-10=5^2\cdot4^2\)

\(\Rightarrow x-10=20^2\)

\(\Rightarrow x-10=400\)

\(\Rightarrow x=410\)

c) \(3\cdot x-2018:2=23\)

\(=3\cdot x-1009=23\)

\(\Rightarrow3\cdot x=1032\)

\(\Rightarrow x=1032:3\)

\(\Rightarrow x=344\)

d) \(280-9\cdot x-x=80\)

\(\Rightarrow280-x\cdot\left(9+1\right)=80\)

\(\Rightarrow280-10\cdot x=80\)

\(\Rightarrow10\cdot x=280-80\)

\(\Rightarrow10\cdot x=200\)

\(\Rightarrow x=20\)

e) \(38\cdot x-12\cdot x-x\cdot16=40\)

\(\Rightarrow x\cdot\left(38-12-16\right)=40\)

\(\Rightarrow x\cdot10=40\)

\(\Rightarrow x=40:10\)

\(\Rightarrow x=4\)

bài 1 cậu ko giải giúp mình dc à

a) 125 . 10 = 1 250

b) 2 021 . 100 = 202 100

c) 1 991 . 25 . 4 = 1 991 . (25 . 4) = 1 991 . 100 = 199 100

d) 3 025 . 125 . 8 = 3 025 . (125 . 8)

= 3 025 . 1 000 = 3 025 000