Math Problem Statement

find the nth term 50,−10,2

Solution

The given sequence is:

50, -10, 2

To find the nth term of this sequence, we'll first determine if it follows a recognizable pattern, such as an arithmetic or geometric sequence.

Step 1: Find the common differences

We subtract each term from the next:

  • 1050=60-10 - 50 = -60
  • 2(10)=122 - (-10) = 12

Since the differences are not constant, the sequence is not arithmetic.

Step 2: Assume a quadratic form

We assume the nth term follows the form: Tn=an2+bn+cT_n = an^2 + bn + c We can now solve for aa, bb, and cc using the first three terms.

For n=1n = 1 (first term): T1=a(1)2+b(1)+c=50    a+b+c=50(1)T_1 = a(1)^2 + b(1) + c = 50 \implies a + b + c = 50 \quad (1)

For n=2n = 2 (second term): T2=a(2)2+b(2)+c=10    4a+2b+c=10(2)T_2 = a(2)^2 + b(2) + c = -10 \implies 4a + 2b + c = -10 \quad (2)

For n=3n = 3 (third term): T3=a(3)2+b(3)+c=2    9a+3b+c=2(3)T_3 = a(3)^2 + b(3) + c = 2 \implies 9a + 3b + c = 2 \quad (3)

Step 3: Solve the system of equations

We now have the system of equations:

  1. a+b+c=50a + b + c = 50
  2. 4a+2b+c=104a + 2b + c = -10
  3. 9a+3b+c=29a + 3b + c = 2

Let's solve this system.

  1. Subtract equation (1) from equation (2): (4a+2b+c)(a+b+c)=1050(4a + 2b + c) - (a + b + c) = -10 - 50 3a+b=60(4)3a + b = -60 \quad (4)

  2. Subtract equation (2) from equation (3): (9a+3b+c)(4a+2b+c)=2(10)(9a + 3b + c) - (4a + 2b + c) = 2 - (-10) 5a+b=12(5)5a + b = 12 \quad (5)

  3. Subtract equation (4) from equation (5): (5a+b)(3a+b)=12(60)(5a + b) - (3a + b) = 12 - (-60) 2a=72    a=362a = 72 \quad \implies a = 36

  4. Substitute a=36a = 36 into equation (4): 3(36)+b=603(36) + b = -60 108+b=60    b=168108 + b = -60 \quad \implies b = -168

  5. Substitute a=36a = 36 and b=168b = -168 into equation (1): 36168+c=5036 - 168 + c = 50 c=50+16836=182c = 50 + 168 - 36 = 182

Step 4: Write the nth term

Now that we have a=36a = 36, b=168b = -168, and c=182c = 182, the nth term is: Tn=36n2168n+182T_n = 36n^2 - 168n + 182

This is the formula for the nth term of the given sequence.


Do you want further details or have any questions?

Here are 5 related questions you might find interesting:

  1. How do you verify if a sequence follows a quadratic pattern?
  2. What are the differences between arithmetic and geometric sequences?
  3. How do you solve a system of linear equations in three variables?
  4. Can you derive the nth term for a geometric sequence instead?
  5. What happens if a sequence follows a cubic pattern?

Tip: When dealing with non-linear sequences, try assuming a polynomial expression for the nth term, then solve using the known values.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Sequences
Systems of Equations

Formulas

Quadratic sequence formula: T_n = an^2 + bn + c
Solving systems of linear equations

Theorems

Solving systems of equations using substitution and elimination

Suitable Grade Level

Grades 9-11