ta có :

ts của a=tử số của b

mà ms của a<ms của b

suy ra a>b

sai bét

Gọi số đó là a. => a+1 chia hết cho 2;3;4;5;6;7;8;9;10 => a+1 thuộc BC(2;3;4;5;6;7;8;9;10) nhưng vì a nhỏ nhất nên a+1 = BCNN(2;3;4;5;6;7;8;9;10)=2520 => a = 2520 -1 => a = 2519

Trả lời:

gọi số nguyên dương nhỏ nhất phải tìm là x 
Theo đề cho thì x+1 = BCNN(2,3,4,5,6,7,8,9,10)=2520 
x = 2519 
Vậy số nguyên dương nhỏ nhất là 2519 
 

a) \(\dfrac{8}{40}+\dfrac{-36}{45}=\dfrac{1}{5}+\dfrac{-4}{5}=\dfrac{1-4}{5}=-\dfrac{3}{5}\)

b) \(\dfrac{3}{5}+\dfrac{4}{-7}=\dfrac{3}{5}-\dfrac{4}{7}=\dfrac{21-20}{35}=\dfrac{1}{35}\)

c, d) giống a, b.

e) \(\dfrac{4}{9}-\dfrac{-5}{6}=\dfrac{4}{9}+\dfrac{5}{6}=\dfrac{8+15}{18}=\dfrac{23}{18}\)

f) \(\dfrac{6}{7}+\dfrac{1}{7}\cdot\dfrac{2}{7}+\dfrac{1}{7}\cdot\dfrac{5}{7}=\dfrac{6}{7}+\dfrac{2}{49}+\dfrac{5}{49}=1\)

g) \(\dfrac{4}{9}\cdot\dfrac{13}{3}-\dfrac{4}{3}\cdot\dfrac{40}{9}=\dfrac{52}{27}-\dfrac{160}{27}=-4\)

h) \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)=\dfrac{16}{7}-\left(\dfrac{4}{3}+\dfrac{8}{7}\right)=\dfrac{16}{7}-\dfrac{52}{21}=-\dfrac{4}{21}\)

i) \(\left(10\dfrac{2}{9}+2\dfrac{3}{5}\right)-6\dfrac{2}{9}=\left(\dfrac{20}{9}+\dfrac{6}{5}\right)-2\cdot\dfrac{2}{3}=\dfrac{154}{45}-\dfrac{4}{3}=\dfrac{94}{45}\)

k) \(\dfrac{7}{19}\cdot\dfrac{8}{11}+\dfrac{7}{19}\cdot\dfrac{3}{11}-\dfrac{26}{19}=\dfrac{56}{209}+\dfrac{21}{209}-\dfrac{26}{19}=-1\)

a)\(\dfrac{8}{40}+\dfrac{-36}{45}=\dfrac{1}{5}+\dfrac{-36}{45}=\dfrac{9}{45}+\dfrac{-36}{45}=\dfrac{-27}{45}\)

b)

\(\dfrac{3}{5}+\dfrac{4}{-7}=\dfrac{3}{5}+\dfrac{-4}{7}=\dfrac{21}{35}+\dfrac{-20}{35}=\dfrac{1}{35}\)

c)\(\dfrac{8}{40}+\dfrac{-36}{45}=\dfrac{1}{5}+\dfrac{-36}{45}=\dfrac{9}{45}+\dfrac{-36}{45}=\dfrac{-27}{45}\)

d)

\(\dfrac{3}{5}+\dfrac{4}{-7}=\dfrac{3}{5}+\dfrac{-4}{7}=\dfrac{21}{35}+\dfrac{-20}{35}=\dfrac{1}{35}\)

(chiều mình làm tiếp!!!)

1/2+2/3+3/4+4/5+5/6+6/7+7/8+8/9+9/10x9/10

=9/10x(1/2+2/3)+(3/4+4/5)+(5/6+6/7)+(7/8+8/9)

=9/10x(1/3+3/5+5/7+7/9)

9/10x(1/3+3/5)+(5/7+7/9)

=9/10x1/5+5/9

9/50+5/9

=10

Bn Long làm đúng rồi bn   nguyễn kim arica cứ làm theo cách đó là được .

Bn nào thấy đúng thì ủng hộ nha .

\(S=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}.\frac{5}{6}.\frac{6}{7}.\frac{7}{8}.\frac{8}{9}.\frac{9}{10}\)

\(S=\frac{1}{10}\)

học tốt 

S=\(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.......\frac{9}{10}\)

S=\(\frac{1.2.3....9}{2.3.4...10}=\frac{1}{10}\)

Vậy S=\(\frac{1}{10}\)

Bài 6:

a: \(x=-\dfrac{2}{3}-\dfrac{1}{7}=\dfrac{-14-3}{21}=\dfrac{-17}{21}\)

d: \(x=\dfrac{9}{10}\cdot\dfrac{-5}{9}=\dfrac{-1}{2}\)

e: \(\Leftrightarrow x\cdot\dfrac{1}{3}=\dfrac{14}{21}-\dfrac{3}{21}=\dfrac{11}{21}\)

=>x=11/7

Ta có:

1 = \(\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+............+\frac{1}{10}\)(10 phân số \(\frac{1}{10}\))

Mà \(\frac{1}{2}>\frac{1}{10};\frac{2}{3}>\frac{1}{10};............;\frac{9}{10}>10\)

\(\Rightarrow M>1\)

Vậy M > 1

Ta có:

1/2=0,5

2/3>0,6

<=>1/2+2/3>1,1>1

<=>1/2+2/3+3/4+...+9/10>1

a)\(\frac{11^4.6-11^5}{11^4-11^5}:\frac{9^8.3-9^9}{9^8.5+9^8.7}\)

\(=1.6:\frac{9^8.3-9^8.9}{9^8.\left(5+7\right)}\)

\(=6:\frac{9^8.\left(3-9\right)}{9^8.12}\)

\(=6:\frac{9^8.\left(-6\right)}{9^8.12}\)

\(=6:\left(-\frac{6}{12}\right)\)

\(=6:\left(-\frac{1}{2}\right)\)

\(=-12\)

b) 3/5 : ( -1/5-1/6)+3/5:(-1/3-16/15) ( mình chuyển về ps luôn )

=3/5: (-11/30) + 3/5 : (-7/5) 

=3/5:[-11/30+(-7/5)]

=3/5:53/30

=18/53

c) (1/2-13/14):5/7-(-2/21+1/7):5/7

= -3/7:5/7-1/21:5/7

=(-3/7-1/21):5/7

=-10/21:5/7

=-2/3

câu b vá c mình làm tắt nha. chúc bạn học tốt