-233;-199;-153;-119 Find the next two terms and Tn

Mathematics

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Answer

-73, -39

Tn=40n−276+3(−1)n−1T_n = 40n - 276 + 3(-1)^{n-1}

Step-by-step solution

4 steps
  1. Find the differences between consecutive terms.

    Given sequence: −233,−199,−153,−119-233, -199, -153, -119.
    Calculate the first differences:

    • D1=−199−(−233)=−199+233=34D_1 = -199 - (-233) = -199 + 233 = 34
    • D2=−153−(−199)=−153+199=46D_2 = -153 - (-199) = -153 + 199 = 46
    • D3=−119−(−153)=−119+153=34D_3 = -119 - (-153) = -119 + 153 = 34
  2. Identify the pattern in the differences.

    The first differences are 34,46,3434, 46, 34. This indicates an alternating pattern where the differences are 34,46,34,46,…34, 46, 34, 46, \dots.

  3. Find the next two terms.

    Following the pattern, the next difference (D4D_4) will be 46.

    T5=T4+D4=−119+46=−73T_5 = T_4 + D_4 = -119 + 46 = -73

    The subsequent difference (D5D_5) will be 34.

    T6=T5+D5=−73+34=−39T_6 = T_5 + D_5 = -73 + 34 = -39

    The next two terms are −73,−39\boxed{-73, -39}.

  4. Find the general formula for TnT_n.

    The sequence of first differences DkD_k can be expressed as Dk=A+B(−1)kD_k = A + B(-1)^k.
    Using D1=34D_1 = 34 and D2=46D_2 = 46:
    For k=1k=1: A−B=34A - B = 34
    For k=2k=2: A+B=46A + B = 46
    Adding these equations: 2A=80  ⟹  A=402A = 80 \implies A = 40.
    Subtracting the first from the second: 2B=12  ⟹  B=62B = 12 \implies B = 6.
    So, the formula for the differences is Dk=40+6(−1)kD_k = 40 + 6(-1)^k.

    The general term TnT_n is given by Tn=T1+∑k=1n−1DkT_n = T_1 + \sum_{k=1}^{n-1} D_k for n>1n > 1.

    Tn=−233+∑k=1n−1(40+6(−1)k)T_n = -233 + \sum_{k=1}^{n-1} (40 + 6(-1)^k) Tn=−233+∑k=1n−140+6∑k=1n−1(−1)kT_n = -233 + \sum_{k=1}^{n-1} 40 + 6 \sum_{k=1}^{n-1} (-1)^k

    The first sum is 40(n−1)40(n-1).
    The second sum is 6×((−1)n−1−12)6 \times \left( \frac{(-1)^{n-1}-1}{2} \right).

    Tn=−233+40(n−1)+3((−1)n−1−1)T_n = -233 + 40(n-1) + 3((-1)^{n-1}-1) Tn=−233+40n−40+3(−1)n−1−3T_n = -233 + 40n - 40 + 3(-1)^{n-1} - 3 Tn=40n−276+3(−1)n−1T_n = 40n - 276 + 3(-1)^{n-1}

    The formula for TnT_n is Tn=40n−276+3(−1)n−1\boxed{T_n = 40n - 276 + 3(-1)^{n-1}}.

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