Math Problem Statement

Evaluate the summation from j=2 to j=8 of (-3) raised to the power j.

Solution

The expression provided is a summation, specifically:

j=28(3)j\sum_{j=2}^{8} (-3)^j

This means we need to calculate the sum of (3)j(-3)^j for jj ranging from 2 to 8. Let's compute this step by step.

Step-by-Step Calculation:

  1. For j=2j = 2: (3)2=9(-3)^2 = 9

  2. For j=3j = 3: (3)3=27(-3)^3 = -27

  3. For j=4j = 4: (3)4=81(-3)^4 = 81

  4. For j=5j = 5: (3)5=243(-3)^5 = -243

  5. For j=6j = 6: (3)6=729(-3)^6 = 729

  6. For j=7j = 7: (3)7=2187(-3)^7 = -2187

  7. For j=8j = 8: (3)8=6561(-3)^8 = 6561

Summing All Terms:

Now, we add up all these values:

9+(27)+81+(243)+729+(2187)+65619 + (-27) + 81 + (-243) + 729 + (-2187) + 6561

Calculating the Sum:

Let's compute the total:

927+81243+7292187+6561=49239 - 27 + 81 - 243 + 729 - 2187 + 6561 = 4923

So, the value of the sum is 4923.

Would you like more details on this process, or do you have any questions?


Relative Questions:

  1. What is the significance of alternating signs in the summation of powers of a negative number?
  2. How does the exponent affect the behavior of the base 3-3 in the sequence?
  3. Can this summation be represented as a geometric series? If so, how?
  4. What would happen if the lower limit of summation changed from j=2j = 2 to j=1j = 1?
  5. How do different bases affect the overall sum when calculated similarly?

Tip: Always check whether the series or sum has a pattern (like geometric progression), as it can simplify the calculations.

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Math Problem Analysis

Mathematical Concepts

Algebra
Exponents
Summation

Formulas

Sum of powers
(-3)^j

Theorems

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Suitable Grade Level

Grades 9-11