Bài 1: 

1: \(17A=\dfrac{17^{19}+17}{17^{19}+1}=1+\dfrac{16}{17^{19}+1}\)

\(17B=\dfrac{17^{18}+17}{17^{18}+1}=1+\dfrac{16}{17^{18}+1}\)

mà \(17^{19}+1>17^{18}+1\)

nên 17A>17B

hay A>B

2: \(C=\dfrac{98^{99}+98^{10}+1-98^{10}}{98^{89}+1}=98^{10}+\dfrac{1-98^{10}}{98^{89}+1}\)

\(D=\dfrac{98^{98}+98^{10}+1-98^{10}}{98^{88}+1}=98^{10}+\dfrac{1-98^{10}}{98^{88}+1}\)

mà \(98^{89}+1>98^{88}+1\)

nên C>D

18:

a: \(K=2\cdot\dfrac{\sqrt{a}-\sqrt{a}+1}{\sqrt{a}\left(\sqrt{a}-1\right)}\cdot\dfrac{a\left(a-1\right)}{\sqrt{a}+1}\)

\(=\dfrac{2\sqrt{a}\left(\sqrt{a}+1\right)}{\sqrt{a}+1}=2\sqrt{a}\)

b: K=căn 2012

=>căn 4a=căn 2012

=>4a=2012

=>a=503

Lời giải:

$31^{14}<34^{14}=2^{14}.17^{14}< 2^{16}.17^{14}=(2^4)^4.17^{14}=16^4.17^{14}< 17^4.17^{14}=17^{18}$

a. -20+5=-15 

b. 7

c. 35 + (-4)= 31 

d. -129-37+29-63= -100-100 = -200 

e. 217 -315-117+215 =100-100=0 

f. 15:(-3)+24:2 = -5 + 12 = 7 

g. (-5).(-7)-3.(14)= 35 - 42 = -7 

H. (-15)x(-129+29) = -15 x -100 =1500 

i. 13 x (-125+25) =13 x -100 = -1300 

k. 37(-135+35) = 37 x -100 = -3700

\(a,\left(2x-5\right)+17=6\)

                    \(2x-5=6-17\)

                    \(2x-5=-11\)

                             \(2x=-11+5\)

                             \(2x=-6\)

                                \(x=-3\)

\(b,10-2.\left(4-3x\right)=-4\)

               \(2.\left(4-3x\right)=10+4\)

               \(2.\left(4-3x\right)=14\)

                        \(4-3x=14:2\)

                        \(4-3x=7\)

                             \(-3x=7-4\)

                             \(-3x=3\)

                                   \(x=-1\)

\(c,-12+3.\left(-x+7\right)=18\)

                     \(3.\left(-x+7\right)=18+12\)

                     \(3.\left(-x+7\right)=30\)

                              \(-x+7=30:3\)

                              \(-x+7=10\)

                                          \(x=7-10\)

                                          \(x=-3\)

\(d,24:\left(3x-2x\right)=-3\)

                      \(24:x=-3\)

                            \(x=24:\left(-3\right)\)

                            \(x=-8\)

\(e,-45:5.\left(-3-2x\right)=3\)

             \(-9.\left(-3-2x\right)=3\)

                         \(27+18x=3\)

                                    \(18x=3-27\)

                                    \(18x=-24\)\

                                         \(x=-\frac{4}{3}\)

sai câu c

I. Write sentences with the cues given

1. Mai / usually / listen / K - pop music / free time.

→ Mai usually listens to K-pop music in her free time.

2. when / I / be / a child / I / enjoy / play / computer games

→ When I was a child, I enjoyed playing computer games.

3. my father / spend / most / spare time / look after / the garden

→ My father spends most of his spare time looking after the garden.

4. watching TV / most / popular / leisure activity / Britain ?

→ Is watching TV the most popular leisure activity in Britain?

5. many teenagers / addicted / the Internet / computer games 

→ Many teenagers are addicted to the Internet and computer games.

6. she / get / hooked / the medical drama / after / watch / the first people 

→ She got hooked on the medical drama after watching the first episode.

7. most / my friends / prefer / play sports / to / surf the net

→ Most of my friends prefer to play sports rather than surf the net.

8. today's world  / teenagers / rely / technology / more / the past 

→ In today's world, teenagers rely on technology more than in the past

II. Write the second sentences so that it has a similar meaning to the first one

1. It takes us more than two hours to see the film " Avatar "

→ The film " Avatar " requires more than two hours of our time to watch.

2. She likes to hang out with friends on Saturday evening

→ She's interested in socializing with friends on Saturday evening

Bài đó ổn rồi ạ nhưng mà câu cuối là breathable nhé

đề hỏi gì vậy em