1 / 5

Properties of Arithmetic and Geometric Sequences

Learn about the properties of arithmetic and geometric sequences using general terms formula and common differences and ratios. Explore how sequences change and continue based on multiplication and addition.

blackmon
Download Presentation

Properties of Arithmetic and Geometric Sequences

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Use the formula of general term to find the common difference of the new sequence. Then, show that the new sequence is also an arithmetic sequence. More about the properties of arithmetic and geometric sequences: • If T(1), T(2), T(3), ...is an arithmetic sequence, then • kT(1)+m, kT(2)+m, kT(3)+m, ...is also an arithmetic sequence. 18.Arithmetic and Geometric Sequences Let d be the common difference of the arithmetic sequence then d = T(n+1)－T(n). T(1), T(2), T(3), ... , Each term of the sequence is multiplied by k, and m is added, then the sequence kT(1), kT(2), kT(3), ... can be obtained. then the sequence kT(1)+m, kT(2)+m, kT(3)+m, ... can be obtained. Let Q(n) be the general term of the new sequence, then Q(n+1)－Q(n) = [kT(n+1)+m]－[kT(n)+m] [kT(n)+m] Remove the square brackets = kT(n+1)+m－ kT(n)－m = k[T(n+1)－T(n)] Factorize = kd ∵ kdis a constant ∴kT(1)+m, kT(2)+m, kT(3)+m, ...is also an arithmetic sequence

  2. More about the properties of arithmetic and geometric sequences: • If T(1), T(2), T(3), ...is an arithmetic sequence, then • kT(1)+m, kT(2)+m, kT(3)+m, ...is also an arithmetic sequence. E.g. 18.Arithmetic and Geometric Sequences If the common difference of the arithmetic sequence a1, a2, a3, ... is d, prove that 3a1+5, 3a2+5, 3a3+5, ... is an arithmetic sequence, and hence, find itscommon difference. The common difference of the arithmetic sequence a1, a2, a3, ... is d, then d = an+1－an. Each term is multiplied by 3, and 5 is added, then the sequence 3a1+5, 3a2+5, 3a3+5, ... can be obtained. According to the property of arithmetic sequence, 3a1+5, 3a2+5, 3a3+5, ...is also an arithmetic sequence. The common difference of the new sequence = (3an+1+5)－(3an+5) = 3an +1+5－3an－5 = 3(an +1－an) = 3d

  3. Use the formula of general term to find the common ratio of the new sequence. Then, show that the new sequence is also a geometric sequence. More about the properties of arithmetic and geometric sequences: (b) If T(1), T(2), T(3), ...is a geometric sequence, then kT(1), kT(2), kT(3), ...is also a geometric sequence (where k  0). kT(n+1) kT(n+1) = = T(n+1) kT(n) kT(n) T(n+1) then r = . = T(n) T(n) Q(n+1) then Q(n) 18.Arithmetic and Geometric Sequences Let r be the common ratio of the geometric sequence T(1), T(2), T(3), ... , Each term of the sequence is multiplied by k (k0), then the sequence kT(1), kT(2), kT(3), ... can be obtained. Let Q(n) be the general term of the new sequence, Reduce the fraction The common ratio of the geometric sequence = r ∴kT(1), kT(2), kT(3), ...is also a geometric sequence

  4. More about the properties of arithmetic and geometric sequences: (b) If T(1), T(2), T(3), ...is a geometric sequence, then kT(1), kT(2), kT(3), ...is also a geometric sequence (where k  0). E.g. 64 = 16 ∴T(n) = 4(4)n－1 = 4n 18.Arithmetic and Geometric Sequences (i) Prove that 4, 16, 64, 256, 1 024, ... is a geometric sequence. Hence, find the general term T(n) of the sequence. T(3) T(4) T(2) T(3) T(2) T(4) 256 16 Prove: = = = = = = 4 4 4 4 = = T(3) T(1) T(2) T(1) 64 4 T(2) T(3) The common ratio of the geometric sequence ∴ 4, 16, 64, 256, 1 024, ...is a geometric sequence

  5. More about the properties of arithmetic and geometric sequences: (b) If T(1), T(2), T(3), ...is a geometric sequence, then kT(1), kT(2), kT(3), ...is also a geometric sequence (where k  0). E.g. 18.Arithmetic and Geometric Sequences (ii) If each term of the sequence in part (i) is multiplied by 2, then a new sequence is obtained. Find the general term Q(n) of the new sequence. Q(2) Q(5) Q(3) Q(4) 4 = = = = Q(1) Q(4) Q(2) Q(3) Each term is multiplied by 2, then the sequence 8, 32, 128, 512, 2 048, ... can be obtained. According to the property of geometric sequence, 8, 32, 128, 512, 2 048, ... is also a geometric sequence. The common ratio of the geometric sequence The common ratio of the new sequence is 4. ∴Q(n) = 8(4)n－1= 2(4)n

More Related