The process of finding the 20th term of arithmetic sequence 8,5,2, - 1

RELATED INFORMATIONS

• 1. Find 2,5,8,11 The 33rd term of this arithmetic sequence The formula of addition, subtraction, multiplication and division
• 2. What is the 20th term of the arithmetic sequence 8,5,2
• 3. It is known that: as shown in the figure, in RT △ ABC, ∠ C = 90 ° and ∠ a = 30 ° take AB and AC as edges respectively, and make equilateral △ Abe and equilateral △ ACD on the outside of △ ABC, de and ab intersect with F, proving: EF = FD
• 4. As shown in the figure, △ Abe and △ ACD are respectively formed by △ ABC folding along AB and AC sides. If ∠ BAC = 150 °, then ∠ DAB =, ∠ DAE= Why
• 5. Taking the two right sides AB and BC of the right triangle ABC as one side, make the equilateral triangle △ Abe and equilateral △ BCF outward respectively, connecting EF and EC. Try to explain: (1) EF = EC; (2) EB ⊥ CF
• 6. Taking the two right sides AB and BC of the right triangle ABC as one side, make the equilateral triangle △ Abe and equilateral △ BCF outward respectively, connecting EF and EC. Try to explain: (1) EF = EC; (2) EB ⊥ CF
• 7. Known: as shown in the figure, take two right angle sides AB and BC of RT △ ABC as sides to make equilateral △ Abe and equilateral △ BCF, connect EF and EC, please explain EF = EC
• 8. In the triangle ABC, CD is high, e is the midpoint of CD, the extension line of AE intersects CB at point F, AE = CE and AF is vertical to CB. If EF = 1, then AE
• 9. As shown in the figure, in RT △ ABC, ∠ B = 90 °, ab = 1, BC = 12, take point C as the center, CB as the radius of arc intersection Ca at point D; take point a as the center, ad as the radius of arc intersection AB at point E. (1) find the length of AE; (2) take points a and E as the center, AB length as the radius of arc, two arcs intersect at point F (F and C are on both sides of AB), connect AF and EF, let the circle where EF intersects de at point G, connect AG, try to guess Think about the size of EAG and explain the reason
• 10. In triangle ABC, D is the point on AC, passing through point D as de parallel to CB, intersecting point AB at point E, and the area ratio of triangle ade to triangle ace is 1:16
• 11. Arithmetic sequence 8, 5, 2 Item 20 of the report is______ ．
• 12. From 1, 2, 3 How many different arithmetic sequences are there if you take any three different numbers from the 20 numbers of, 20 to form the arithmetic sequence
• 13. Insert three numbers between 20 and 70, so that these five numbers become arithmetic sequence. What are the three numbers inserted?
• 14. Will 1, 2 If the nine numbers are divided into three groups averagely, the probability that the three numbers in each group can form an arithmetic sequence is () A. 156B. 170C. 1336D. 1420
• 15. Choose three different numbers from 1,2,3... 20, and make these three numbers into arithmetic sequence. How many pairs of arithmetic sequence are there?
• 16. From the set {1, 2, 3 , 20} and make the three numbers into an increasing arithmetic sequence, then the sequence has the same number______ Group
• 17. In known arithmetic sequence an, the sum of the first 30 items is 50, and the sum of the first 50 items is 30, then the sum of the first 80 items is
• 18. Given that the sum of the first five items of an arithmetic sequence is 120, the sum of the last five items is 180, and the sum of each item is 360, how many items are there in this sequence
• 19. If the sum of the first n terms of the arithmetic sequence {an} is Sn, and S4 = 20, sn-4 = 60, Sn = 120, then n=______ ．
• 20. Given that the first term of an arithmetic sequence is - 20 and the 50th term is 120, find the sum of its first 50 terms?