22A         23A

not me

giup voi moi nguoi

a, 23 + ( -77 ) + ( -23 ) + 77

= [ 23 + ( -23 ) ] + [ ( -77 ) + 77 ]

= 0 + 0 = 0

b, ( -2020 ) + 2021 + 21 + ( -22 )

= ( - 2020 ) + 2021 + 21 + ( -21 ) + ( -1 )

= [ ( -2020 ) + 2021 + ( -1 ) ] + [ 21 + ( -21 ) ]

= 0 + 0 = 0

a) 23 + (-77) + (-23) + 77 =
[23 + (-23)] + [(-77) + 77]
=0+0=0
b) (-2 020) + 2 021 + 21 + (-22)
=[(-2 020) + 2 021] + [21 + (-22)]
=1+(-1)
= 0. 

22. A lot of fish has died recently because of the _____________ water in this lake.

A. contaminating B. contaminated C. contaminate D. contaminant

23. If the air was clean, we _____________ have to wear masks when going out.

A. wouldn’t B. won’t C. would D. will

24. If I _____________ you, I _____________ water from that dirty tap

A. am - will drink B. am - won’t drink C. were - would drink D. were - wouldn’t drink 2

5. If he _____________ trash around his garden, the garden would look very nice now.

A. will throw B. would throw C. didn’t throw D. doesn’t throw

26. Price and availability are the _____________ factors that will determine product success.

A. critical B. musical C. physical D. medical

27. If it rains, we _____________ the match.

A. cancel B. will cancel C. cancelled D. cancelling

28. If I were a tree, I _____________ the rain.

A. love B. loved C. will love D. would love

29. The decor inside the house was very_____________.

A. fantastic B. electric C. mechanic D. artistic

30. If she _____________ late, we will go without her.

A. am B. is C. was D. were

31. If I _____________ where she lived, I would go and see her.

A. know B. knows C. to know D. knew

32. We need to be more _____________ about this problem.

A. scientific B. majestic C. domestic D. alphabetic

33. The election campaign has been focused mainly on _____________ issues.

A. dialectical B. energetic C. domestic D. conical

34. If I _____________ the lottery, I would be a millionaire.

A. win B. wins C. winning D. won

35. I will discuss that problem with him if I _____________ him tomorrow.

A. see B. sees C. to see D. seeing

36. If I knew Chinese, I _____________ for job in China.

A. will apply B. would apply C. will be applied D. would be applied

37. She was unable to find a _____________ job.

A. important B. importantly C. permanent D. permanently

38. Any company found to be breaking these rules will be heavily _____________.

A. fined B. done C. made D. got

39. These figures are for _____________ purposes only

. A. illustrate B. illustrating C. illustrative D. illustration

40. I would go jogging with Mark if he _____________ here today.

A. is B. will be C. were D. would be

41. Many species of wildlife are becoming extinct, _____________ the rainforests are being destroyed.

A. therefore B. since C. consequently D. so

42. Hemp can be used to make paper, _____________ it could reduce the need for logging.

A. consequently B. due to C. so D. since

43. _____________ logging provides jobs and profits, the government is reluctant to control it.

A . So B. Consequently C. Since D. Due to

44. Hemp was grown throughout history_____________ its versatility; it can be used to make many different things.

A. due to B. because C. since D. as a result

45. Hemp is related to the marijuana plant; _____________ it is illegal in many countries.

A. so B. due to C. as a result D. because

46. The polluted chemical waste was dumped into the ocean; _____________,the mass of fish died.

A. because B. as C. because of D. consequently

47. It was guessed that the fish died_____________ a powerful toxin in the sea water.

A. because of B. because C. since D. as a result

48. Many species in BC are threatened _____________ logging.

A. so B. because C. since D. due to

49. Smoking can_____________ heart disease.

A. lead to B. create C. causes D. due to

50. Radioactive pollution is increasing _____________ the increased use of radioactivity.

A. as B. since C. because of D. because

Mình chỉ sửa cho bạn Hải là câu 24 phải là D nha vì nếu là would drink thì chả lẽ là uống nước bẩn?Và câu 26 phải là medical nha, bài này cô chữa cho mình nên không sai đâu.

\(B=2+2^2+2^3+2^4+...+2^{99}+2^{100}=2\left(1+2^2+2^3+2^4\right)+...+2^{96}\left(1+2^2+2^3+2^4\right)=2.31+2^6.31+...+2^{96}.31=31\left(2+2^6+...+2^{96}\right)⋮31\)

B=2+22+23+24+...+299+2100=2(1+22+23+24)+...+296(1+22+23+24)=2.31+26.31+...+296.31=31(2+26+...+296)⋮31

b) 917-(417-65)

= 917- 352

= 565

c) 31-[26-(2017+35)]

=  31-[26-2052]

= 31- (-2026)= 31+2026= 2057

g) -418-{-218-[-118-(-131)]+2017}

= -418-{-218-[-118+131]+2017}

= -418-{-218-13+2017}

= -418-1786

= -2204

Các câu còn lại thì bạn làm tương tự nha!( nhân chia trước, cộng trừ sau, trong ngoặc làm trước ngoài ngoặc làm sau)

\(B=2+2^2+2^3+...+2^{100}\)

\(\Rightarrow2B=2^2+2^3+2^4+...+2^{101}\)

\(\Rightarrow2B-B=2^2+2^3+2^4+...+2^{101}-2-2^2-2^3-...-2^{100}\)

\(\Rightarrow2B-B=2^{101}-2\)

bài 1

2¹⁰¹ - 2

\(A=1+3+3^2+3^3+...+3^{99}\\ \Rightarrow A=\left(1+3+3^2+3^3\right)+\left(3^4+3^5+3^6+3^7\right)+...+\left(3^{96}+3^{97}+3^{98}+3^{99}\right)\)

\(\Rightarrow A=\left(1+3+3^2+3^3\right)+3^4\left(1+3+3^2+3^3\right)+...+3^{96}\left(1+3+3^2+3^3\right)\)

\(\Rightarrow A=\left(1+3+3^2+3^3\right)\left(1+3^4+...+9^{96}\right)\)

\(\Rightarrow A=40\left(1+3^4+...+9^{96}\right)⋮40\)

\(a,\Rightarrow2A=2+2^2+...+2^{2011}\)

\(\Rightarrow2A-A=2+2^2+...+2^{2011}-2^0-2-..-2^{2010}\)

\(\Rightarrow A=2^{2011}-1=B\)

\(b,A=2019.2011=\left(2010-1\right)\left(2010+1\right)=\left(2010-1\right).2010+\left(2010-1\right)=2010^2-2010+2010-1=2010^2-1< 2010^2=B\)

\(a,\Rightarrow2A=2^1+2^2+...+2^{2011}\\ \Rightarrow2A-A=A=2^{2011}-2^0=2^{2011}-1=B\)

\(b,A=\left(2010-1\right)\left(2010+1\right)=2010^2+2010-2010-1=2010^2-1< 2010^2=B\)

( -23 ) + 105 = 105 - 23

                    = 82

78 + ( -123 ) = -( 123 - 78 ) 

                    = -45

( -23) + 13   = -( 23 - 13 )

                   = -10

( -23 ) + ( -13 ) = -( 23 + 13 )

                        = - 36

( -75 ) + ( -50 ) = -( 75 + 50 )

                        = -125

( -20 ) + | -88 | = ( -20 ) + 88

                       = 88 - 20

                       = 68

| -37 | + (-|15|) = 37 + ( -15 )

                        = 37 - 15

                        = 22

(-|-22|) + ( -|16|) = ( -22 ) + ( -16 )

                          = -38

( -23 ) + 13 + ( -17 ) + 57 = [(-23) + 13 ] + [(-17) + 57 ]

                                        = 10 + 40

                                        = 50

(-123) + |-13| + (-7) = (-123) + 13 + (-7)

                               = 110 + (-7)

                               = 103

|0| + |45| + (-|-455|) + |-796| = 0 + 45 + (-455) + 796

                                             = [ 796 + (-455) ] + 45

                                             = 341 + 45

                                             = 386

Tui làm chi tiết lắm rồi đó ^_^

\(=-23-\left(-105\right)=82\)

\(=78-123=-45\)

\(=-23-\left(-13\right)=-10\)

\(=-36\)

\(=-125\)

\(=-20-\left(-88\right)=68\)

Phần dưới tự làm nha

(-23)+105=82

78+(-123)=(-45)

(-23)+13=(-10)

(-23)+(-13)=(-36)