Bài 2: 

Ta có: \(16x+40=10\cdot3^2+5\left(1+2+3\right)\)

\(\Leftrightarrow16x+40=90+30\)

\(\Leftrightarrow16x=80\)

hay x=5

Bài 1 :

[( 35 - 5 ) : 3 ]³ + 3

= [30 : 3]³ + 3

= 10³ + 3

= 1000 + 3

= 1003

Đây nha bạn!!!

Chúc bạn học tốt!!!

Câu này dễ quá

Bài 7:

7.1: I là trung điểm của AB

=>\(AB=2\cdot IA=4\left(cm\right)\)

7.2:

C nằm giữa A và B

=>AC+CB=AB

=>CB=10-8=2(cm)

C là trung điểm của NB

=>NC=CB=2cm

C là trung điểm của NB

=>\(NB=2\cdot NC=2\cdot2=4\left(cm\right)\)

Bài 6:

a: \(\dfrac{4}{5}=\dfrac{4\cdot6}{5\cdot6}=\dfrac{24}{30}\)

\(\dfrac{8}{15}=\dfrac{8\cdot2}{15\cdot2}=\dfrac{16}{30}\)

\(-\dfrac{3}{2}=\dfrac{-3\cdot15}{2\cdot15}=-\dfrac{45}{30}\)

b: \(2=\dfrac{2\cdot45}{45}=\dfrac{90}{45}\)

\(\dfrac{-10}{5}=\dfrac{-10\cdot9}{5\cdot9}=\dfrac{-90}{45}\)

\(\dfrac{7}{-9}=\dfrac{-7}{9}=\dfrac{-7\cdot5}{9\cdot5}=\dfrac{-35}{45}\)

c: \(\dfrac{3}{-2}=\dfrac{-3}{2}=\dfrac{-3\cdot6}{2\cdot6}=\dfrac{-18}{12}\)

\(\dfrac{5}{-6}=\dfrac{-5}{6}=\dfrac{-5\cdot2}{6\cdot2}=\dfrac{-10}{12}\)

\(\dfrac{-6}{4}=\dfrac{-6\cdot3}{4\cdot3}=\dfrac{-18}{12}\)

d: \(-\dfrac{1}{2}=\dfrac{-1\cdot15}{2\cdot15}=\dfrac{-15}{30}\)

\(\dfrac{4}{3}=\dfrac{4\cdot10}{3\cdot10}=\dfrac{40}{30}\)

\(\dfrac{6}{-5}=\dfrac{-6}{5}=\dfrac{-6\cdot6}{5\cdot6}=\dfrac{-36}{30}\)

bài 5:

a: \(\dfrac{3}{4}=\dfrac{9}{12};\dfrac{-3}{12}=\dfrac{-3}{12};\dfrac{-2}{3}=-\dfrac{8}{12};\dfrac{-1}{-6}=\dfrac{1}{6}=\dfrac{2}{12}\)

mà -8<-3<2<9

nên \(-\dfrac{8}{12}< -\dfrac{3}{12}< \dfrac{2}{12}< \dfrac{9}{12}\)

=>\(\dfrac{-2}{3}< \dfrac{-3}{12}< \dfrac{-1}{-6}< \dfrac{3}{4}\)

b: Ta có: \(\dfrac{-7}{9}=\dfrac{-28}{36};\dfrac{-1}{3}=\dfrac{-12}{36};-1=-\dfrac{36}{36}\)

mà -36<-28<-12

nên \(-1< -\dfrac{28}{36}< -\dfrac{12}{36}\)

=>\(-1< \dfrac{-7}{9}< -\dfrac{1}{3}< 0\)

\(\dfrac{5}{12}=\dfrac{15}{36};\dfrac{-1}{-4}=\dfrac{1}{4}=\dfrac{9}{36}\)

mà 9<15

nên \(0< \dfrac{1}{4}< \dfrac{5}{12}\)

=>\(-1< -\dfrac{7}{9}< -\dfrac{1}{3}< 0< \dfrac{1}{4}< \dfrac{5}{12}\)

c: \(\dfrac{-1}{-2};0;\dfrac{3}{10};1;\dfrac{-2}{-5};\dfrac{3}{-4}\)

\(-\dfrac{3}{4}< 0\)

\(\dfrac{-1}{-2}=\dfrac{1}{2}=\dfrac{5}{10};\dfrac{3}{10}=\dfrac{3}{10};1=\dfrac{10}{10};\dfrac{-2}{-5}=\dfrac{4}{10}\)

mà 3<4<5<10

nên \(\dfrac{3}{10}< \dfrac{4}{10}< \dfrac{5}{10}< \dfrac{10}{10}\)

=>\(0< \dfrac{3}{10}< \dfrac{-2}{-5}< \dfrac{-1}{-2}< 1\)

=>\(-\dfrac{3}{4}< 0< \dfrac{3}{10}< \dfrac{-2}{-5}< \dfrac{-1}{-2}< 1\)

d: \(-\dfrac{37}{150}=\dfrac{-37}{150};\dfrac{17}{-50}=\dfrac{-17}{50}=\dfrac{-51}{150}\)

\(\dfrac{23}{-25}=\dfrac{-23}{25}=\dfrac{-138}{150};\dfrac{-7}{10}=\dfrac{-105}{150};\dfrac{-2}{5}=-\dfrac{60}{150}\)

mà -138<-105<-60<-51<-37

nên \(-\dfrac{138}{150}< -\dfrac{105}{150}< -\dfrac{60}{150}< -\dfrac{51}{150}< -\dfrac{37}{150}\)

=>\(\dfrac{23}{-25}< \dfrac{-7}{10}< \dfrac{-2}{5}< \dfrac{-17}{50}< \dfrac{37}{-150}\)

bài 4:so sánh

5/2 lớn hơn 3/7

4/3 lớn hơn,3/2 lớn hơn 

bài 6:rút gọn các phân số sau:

3/9=1/3      9/12=3/4          8/18=4/9         60/36=10/6         17/34=1/2              17/51=1/3           35/100=7/20           25/100=1/4                  8/1000=1/125                 24/30=4/5           18/54=1/3           72/42=12/7

đay nhé mk chưa làm hết đc bn viết liền quá mk nhìn khó mà mk hỏi bài 7 là nhân hay cộng vậy?

4 phần 5 trừ 11 phần 5 =

1 + 1 = 2

2 + 2 = 4

3 + 3 = 6

4 + 4 = 8

5 + 5 = 10

Lời giải:

a. 

$(25-2x)^3:5-3^2=4^2$

$(25-2x)^3:5=4^2+3^2=25$

$(25-2x)^3=25.5=5^3$

$\Rightarrow 25-2x=5$

$\Rightarrow 2x=20$

$\Rightarrow x=10$

b.

$2.3^x=10.3^{12}+8.27^4=10.3^{12}+8.3^{12}=18.3^{12}=2.3^{14}$

$\Rightarrow 3^x=3^{14}$

$\Rightarrow x=14$

Bài 1:

a) \(=\dfrac{8}{15}\left(\dfrac{7}{13}+\dfrac{6}{13}\right)=\dfrac{8}{15}.1=\dfrac{8}{15}\)

b) \(=\dfrac{3.3-7-2.4}{12}=-\dfrac{6}{12}=-\dfrac{1}{2}\)

Bài 2:

 \(\dfrac{x}{2,7}=-\dfrac{2}{3,6}\Rightarrow x=\dfrac{\left(-2\right).2,7}{3,6}\Rightarrow x=-\dfrac{3}{2}\)

Bài 3:

\(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{x+y}{2+5}=-\dfrac{21}{7}=-3\)

\(\Rightarrow\left\{{}\begin{matrix}x=\left(-3\right).2=-6\\y=\left(-3\right).5=-10\end{matrix}\right.\)

Bài 2:

a: 5/7-3/7x=1

=>3/7x=-2/7

hay x=-2/3

b: \(x+\dfrac{2}{3}=\dfrac{-1}{12}\cdot\dfrac{-4}{5}=\dfrac{1}{15}\)

=>x=1/15-2/3=-9/15=-3/5

c: \(x-4=\dfrac{-14}{35}:\dfrac{7}{5}=\dfrac{-14}{35}\cdot\dfrac{5}{7}=\dfrac{-70}{245}=\dfrac{-2}{7}\)

=>x=4-2/7=26/7

Bài 2: 

a: 5/4<7/4

b: 2/3=34/51

9/17=27/51

mà 34>27

nên 2/3>9/17

Bài 3: 

a: 1/3+3/8=8/24+9/24=17/24

b: 7/6+5/18=21/18+5/18=26/18=13/9

Từng bài 1 thôi nhé

Bài 2: 

a: 5/4<7/4

b: 2/3=34/51

9/17=27/51

mà 34>27

nên 2/3>9/17

Bài 3: 

a: 1/3+3/8=8/24+9/24=17/24

Bài 3:

\(\Rightarrow n-3\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{4;2;5;1;7;-1\right\}\)