\(\overline{abc}\times9=\overline{1abc}\Leftrightarrow9\overline{abc}=1000+\overline{abc}\Leftrightarrow8\overline{abc}=1000\Leftrightarrow\overline{abc}=125.\)

abc x 9 = 1abc

abc  x 9 = 1000 + abc

abc  x  9 - abc = 1000

abc x ( 9-1 ) = 1000

abc x 8 = 1000

abc = 1000 : 8

abc = 125

1abc=1000+abc

Ta có abc chia hết cho abc, vạy số dư của 1000 khi chia cho abc cũng là số dư của 1abc khi chia cho abc

Vậy 1000 chia abc dư 3

=> 997 chia hết cho abc

abc thuộc Ư(997)={1;997}, 997 là snt

abc có 3 chữ số nên abc=997

abc=997

\(\dfrac{x+1}{3\left(x-1\right)^2\left(x+1\right)}và\dfrac{1-x}{3\left(x-1\right)^2\left(x+1\right)}\)

a: \(x-40\%\cdot x=\frac13\cdot\frac{-9}{5}\)

=>\(x-0,4x=\frac{-3}{5}\)

=>0,6x=-0,6

=>x=-1

b: \(\frac{x-3}{10}-\frac{x-3}{15}=\frac{x-3}{12}-\frac{x-3}{18}\)

=>\(\left(x-3\right)\left(\frac{1}{10}-\frac{1}{15}-\frac{1}{12}+\frac{1}{18}\right)=0\)

=>x-3=0

=>x=3

c: \(\frac{1}{2\cdot4}+\frac{1}{4\cdot6}+\cdots+\frac{1}{\left(2x-2\right)\cdot2x}=\frac18\)

=>\(\frac{2}{2\cdot4}+\frac{2}{4\cdot6}+\cdots+\frac{2}{\left(2x-2\right)\cdot2x}=\frac28=\frac14\)

=>\(\frac12-\frac14+\frac14-\frac16+\cdots+\frac{1}{2x-2}-\frac{1}{2x}=\frac14\)

=>\(\frac12-\frac{1}{2x}=\frac14\)

=>\(\frac{1}{2x}=\frac12-\frac14=\frac14\)

=>2x=4

=>x=2

d: \(x-25\%\cdot x=60-x+0,25x\)

=>x-0,25x=60-0,75x

=>0,75x+0,75x=60

=>1,5x=60

=>x=40

e: \(x^2\left(x-0,2\right)^2+\left(\frac{1}{25}-x^2\right)=0\)

=>\(x^2\cdot\left(x-\frac15\right)^2-\left(x-\frac15\right)\left(x+\frac15\right)=0\)

=>\(\left(x-\frac15\right)\left\lbrack x^2\left(x-\frac15\right)-x-\frac15\right\rbrack=0\)

=>\(\left(x-\frac15\right)\left(x^3-\frac15x^2-x-\frac15\right)=0\)

=>\(x-\frac15=0\) hoặc \(x^3-\frac15x^2-x-\frac15=0\)

=>\(x=\frac15\) hoặc x≃1,19 hoặc x≃-0,77 hoặc x≃-0,22

1.C

2.B

3.C

4.A

5.B

6.C

7.C

8.A

9.B

10.C

11.D

12.B

13.B

1.C

2.B

3.C

4.A

5.B

6.C

7.C

8.A

9.B

10.C

11.D

12.B

13.B

D

I want to visit Da Nang, a beautiful city in central Viet Nam. It has many attractions like the Golden Bridge and Marble Mountains. It is famous for stunning beaches and fresh seafood. I like it because the atmosphere is very relaxing and the people are friendly.

26D 27B 28D 29C 30D 31A 32B 33B 34D 35C