In the explicit formula "d(n-1)" means "the common difference times (n-1), where n is the integer ID of term's location in the sequence." In the iterative formula, "a(n-1)" means "the value of the (n-1)th term in the sequence", this is not "a times (n-1)." Even though they both find the same thing, they each work differently-they're NOT the same form. A + B(n-1) is the standard form because it gives us two useful pieces of information without needing to manipulate the formula (the starting term A, and the common difference B).Īn explicit formula isn't another name for an iterative formula. M + Bn and A + B(n-1) are both equivalent explicit formulas for arithmetic sequences. So the equation becomes y=1x^2+0x+1, or y=x^2+1ītw you can check (4,17) to make sure it's right
Substitute a and b into 2=a+b+c: 2=1+0+c, c=1 Then subtract the 2 equations just produced: Solve this using any method, but i'll use elimination: The function is y=ax^2+bx+c, so plug in each point to solve for a, b, and c. Let x=the position of the term in the sequence Since the sequence is quadratic, you only need 3 terms. Begin by finding the common ratio, r 6 3 2. Example 9.3.1: Find an equation for the general term of the given geometric sequence and use it to calculate its 10th term: 3, 6, 12, 24, 48. that means the sequence is quadratic/power of 2. In fact, any general term that is exponential in n is a geometric sequence. Determine if the following situations describe an arithmetic or geometric sequence and if they require a linear or exponential growth model Write an explicit formula for the sequence that models the growth for each case. However, you might notice that the differences of the differences between the numbers are equal (5-3=2, 7-5=2). What is the 8th term of the geometric sequence 125, 25, 5, 4.
This isn't an arithmetic ("linear") sequence because the differences between the numbers are different (5-2=3, 10-5=5, 17-10=7) Calculation for the n th n^\text=17 = 5 + 4 ⋅ 3 = 1 7 equals, start color #0d923f, 5, end color #0d923f, plus, 4, dot, start color #ed5fa6, 3, end color #ed5fa6, equals, 17
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