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Arithmetic Sequence. Objectives:. At the end of the study, the student must be able to: define arithmetic sequence; know if a sequence is an arithmetic progression; apply arithmetic sequence in problems; insert arithmetic means between two numbers, and;
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Objectives: At the end of the study, the student must be able to: • define arithmetic sequence; • know if a sequence is an arithmetic progression; • apply arithmetic sequence in problems; • insert arithmetic means between two numbers, and; • get the common difference, first term, and nth term.
What is it? • A sequence is a set of numbers in a specific order. What this means is that the set of numbers can be put into a one-to-one correspondence with the Counting Numbers (1, 2, 3, 4, ... ). Thus, you can talk about the 1st element (or term) in a sequence or the 10th element in a sequence or the 101st element in a sequence. • An arithmetic sequence is a sequence in which the difference between any two consecutive terms is the same, i.e., the difference is a constant. • It is a sequence in which the difference between two successive terms has a constant (d) which is called the common difference.
General Formula: tn=a+(n-1)d a = first term n = no. of terms d = common difference (term-previous term) tn = nth term
Points to Ponder • The sequence that begins 1, 4, 7, 10, 13, 16, . . . is an arithmetic sequence since the difference between consecutive terms is always 3. • The sequence that begins 8, 6, 4, 2, 0, -2, -4, . . . is an arithmetic sequence since the difference between consecutive terms is always -2. • In order to identify if a pattern is an arithmetic sequence you must examine consecutive terms. If all consecutive terms have a common difference you can conclude that the sequence is arithmetic.
Examples: Find the variables being asked. • 2,7,12 find d and t12 d=5 t12=a+(n-1)d =2+(11-1)5 =2+11(5) =2+55 answer: 57 • 6, 10, 14 find t50 d=40 t50=6+(50-1)4 =6+(49)4 =6+196 =202
3. Find the 15th term of the A.P if the fifth term is 12 and the tenth term is -3 t5= a + (5-1)d t10= a + (10-1)d (a+4d=12)-1 a+4d=12 a+9d=-3 a+4(-3)=12 -a-4d=-12 a-12=12 a+9d=-3 a=24 5d=-15 t15= a +(15-1)d d=-3 =24+14(-3) =14+(-42) = -15
4. Find the value of k if 6-2k, 3k+1, and 5k form an A.P. (3k+1)-(6-2k)=(5k)-(3k+1) 3k+1-6-2k=5k-3k-1 5k-5=2k-1 3k=4 k= 4/3
5. Insert three arithmetic means between 4 and 10 4, t2,t3,t4,10 t2=4+3/2= 5 ½ t5=a +(5-1)d t3=5 ½+3/2=7 10=4+4d t4=7+3/2= 8 ½ 6=4d d=3/2
I. Determine which of the following sequences are in A.P. For those that are in A.P, give the common difference, and the next three terms of the sequence. • 0.1, 0.01, 0.001… • 40, 42, 44, 46… • 5, 8, 11, 14… • 1/3, 1/4, 1/6, 1/12… • 1.2, 1.8, 2.4… • -11, -7, -3, 1… • x+2, 2x+1, 3x… • 1/3, 1, 5/3.. • 5/3, 15/4, 5… • √2, √3, √4, √5…
II. Given the first term (a),and the common difference (d) of an A.P, find the next 5 terms. • a = 2/5 d = 1/10 • a = 1.5 d = 0.3 • a = 3 d = -5 • a = -3 d = 2 • a = x+4 d = x-2
III. Find the common difference and insert four arithmetic means between the given numbers. • 9 and 24 • -25 and 3 • 4 and 179 • 50.1 and 50. 7 • a and a+12 • x + 2 and x + 10
IV. Problem solving. Find the variable being asked. • If 5x – 3, x + 2 and 3x – 11 form an A.P, find x and t21. • If the first term is -4, and the common difference is 3, what term is 116? • The ninth term of an A.P is 15, and the 17th term is 27, find the a and d.
4. The third term of an A.P is 9 and its 7th term is 49, what is the 11th term? 5. A carpenter made a ladder with 16 rungs. The bottom rung is 70 cm. if each succeeding rung is 1 cm shorter than the preceding, how long is the top most rung?
Test I answers: • Not A.P • A.P, d = 2, Next 3 terms = 48, 50, 52 • A.P, d = 3, Next 3 terms = 17, 20, 23 • A.P, d = -1/12, Next 3 terms = 0, -1/12, -1/6 • A.P, d = 0.6, Next 3 terms = 3, 3.6, 4.2 • A.P, d = 4, Next 3 terms = 5, 9, 13 • A.P, d = x-1, Next 3 terms = 4x-1, 5x-2, 6x-3 • A.P, d = 2/3, Next 3 terms = 2 1/3, 3, 3 2/3 • Not A.P • Not A.P
Test II answers: • 1/2, 3/5, 7/10, 4/5, 9/10 • 1.8, 2.1, 2.4, 2.7, 3 • -2, -7, -12, -17, -22 • -1, 1, 3, 5, 7 • 2x+2, 3x, 4x-2, 5x-4, 6x-6
Test III answers: • d = 3, Four arithmetic means = 12, 15, 18, 21 • d = 28/5, Four arithmetic means = -19 2/5, -13 4/5, -8 1/5, -2 3/5 • d = 35, Four arithmetic means = 39, 74, 109, 144 • d = 0.12, Four arithmetic means = 50.22, 50.34, 50.46, 50.58 • d = 12/5, Four arithmetic means = a + 12/5, a + 24/5, a + 36/5, a + 48/5 • d = 8/5, Four arithmetic means = x + 18/5, x + 26/5, x + 34/5, x + 42/5
Test IV answers: • x = 3, t21 = -128 • n = 41st term • d = 3/2, a = 3 • 11th term = 89 • t16 = 55 cm
Prepared by: • Marx Lennin Cabaltican • Bernadette Aubrey Cabrera • Precious Fernandez