Math Problem Statement

Supposons qu’il existe un entier n ≥ 2 tel que u_n = 9 × 10^(n-2) - 10. Il s’agit de prouver que u_{n+1} = …

Solution

The provided image contains a mathematical problem written in French. The statement is as follows:


Translation and Interpretation:

Given:

  • An integer n2n \geq 2,
  • un=9×10n210u_n = 9 \times 10^{n-2} - 10.

Objective:

  • Prove that un+1=u_{n+1} = \dots.

Let me analyze and solve the problem systematically:

1. General Pattern for un+1u_{n+1}

The sequence unu_n is given by: un=9×10n210.u_n = 9 \times 10^{n-2} - 10.

To find un+1u_{n+1}, substitute n+1n+1 into the expression for unu_n: un+1=9×10(n+1)210.u_{n+1} = 9 \times 10^{(n+1) - 2} - 10. Simplify: un+1=9×10n110.u_{n+1} = 9 \times 10^{n-1} - 10.


2. Verify Consistency and Induction

This recurrence relation defines un+1u_{n+1} in terms of nn. It appears the problem may aim to prove this relation using induction or demonstrate how un+1u_{n+1} satisfies the pattern.

Would you like me to continue with an induction proof or provide additional steps for clarity?


Follow-up Questions:

  1. Would you like a step-by-step proof for this relation (e.g., using mathematical induction)?
  2. Should I calculate a few terms of unu_n to validate the pattern?
  3. Would you like an explanation of how this recurrence relates to sequences in general?
  4. Should I interpret additional parts of the image for further problem context?
  5. Would you like an explanation of why 9×10n2109 \times 10^{n-2} - 10 is significant in this sequence?

Tip:

When working with sequences, always calculate the first few terms to observe patterns before diving into formal proofs.

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Math Problem Analysis

Mathematical Concepts

Sequences
Recurrence Relations
Algebra

Formulas

u_n = 9 × 10^(n-2) - 10
u_{n+1} = 9 × 10^(n-1) - 10

Theorems

Basic properties of exponential and recursive sequences

Suitable Grade Level

Grades 10-12