72: √21.3 ²- √225 75: √(3 ²)+(-4) ²-2 √(-5) ²-3 ²

Mấy anh chị giúp em với em mới học nên chưa biết làm

Bài 1: Tính a, (1/2-1/3) mũ 2 b, (3/4 - 5/6) mũ 2 c, (1+1/2-1/3) . (2/3 - 1/2) mũ 2 d, 3 : (1/3 - 1/2) mũ 3 CÁC BN GIÚP MIK VỚI CTLHN LUÔN, VOTE 5 SAO LUÔN

ai giúp cái A=1/2 ²+1/3 ²+1/4 ²+...+1/100 ² chứng minh 1/2<A<1

cos bao nhiêu số tự nhiên có 2 chữ số ko lớn hơn 2020

Giúp mình giải pt sau Cos3x = cosx

Nêu suy nghĩ của em về sự cần thiết của trân trọng cuộc sống (bài văn có mở bài,tb,kb) làm dàiiiiiii giúp e vs ạ ko đc viết ngắn ạ giúp e vs please !!

6. New evidence___________by the city attorney. A. has be discovered B. has been discovered C. are discovered D. will been discovered 7. A special committee___________the dispute. A. is going to settle B. is going to be settled C. going to settling D . will going to be settled 8. You____________by my secretary next week. A. will notify B. would notify C. will be notified D. is going to notified 9. At one time the entire world__________by dinosaurs A has ruled B. was ruled C. will be ruled D. was ruling 10. Mark_______ a lot by his friends, isn't he? A. is influenced B. is influencing C. isn't influenced D. isn’t influencing 11. A few days ago, Tom's car_________ by one of the teenagers in his neighborhood. A. was stealing B. was stole C. has been stolen D. was stolen 12. The wheel__________ thousands of years ago. A. invented B. was invented C. is invented D. has invented 13. I got upset when I _______ in the middle of my story. A. interrupted B. has interrupted C. was being interrupted D. was interrupted 14. Pencils________ at the test, so please bring your own. A. are provided B. will be provided C. won't be provided

1. Tìm x ∈ Q, biết: (x+2) . (x-$\frac{2}{3}$) > 0 2. So sánh: $\frac{-13}{19}$ và $\frac{19}{-23}$

Khi sắp xếp dữ liệu trong excel từ Z -> A xong, mình nhập mấy chữ số vào, sau đó mình muốn trở lại cách sắp xếp như ban đầu mình phải làm gì ạ?