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Mathematics

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: Arithmetic Progression

The sum of the first nn terms of an arithmetic progression is given by Sn=2n2+3nS_n = 2n^2 + 3n. Find the first term and the common difference.

  1. Find the first term (T1T_1).

    The sum of the first term is equal to the first term itself.

    S1=2(1)2+3(1)S_1 = 2(1)^2 + 3(1) S1=2(1)+3S_1 = 2(1) + 3 S1=2+3S_1 = 2 + 3 T1=5T_1 = 5
  2. Find the sum of the first two terms (S2S_2).

    S2=2(2)2+3(2)S_2 = 2(2)^2 + 3(2) S2=2(4)+6S_2 = 2(4) + 6 S2=8+6S_2 = 8 + 6 S2=14S_2 = 14
  3. Find the second term (T2T_2).

    The second term is the sum of the first two terms minus the first term.

    T2=S2−S1T_2 = S_2 - S_1 T2=14−5T_2 = 14 - 5 T2=9T_2 = 9
  4. Find the common difference (dd).

    The common difference is the difference between any term and its preceding term.

    d=T2−T1d = T_2 - T_1 d=9−5d = 9 - 5 d=4d = 4

    The first term is 5\boxed{\textbf{5}} and the common difference is 4\boxed{\textbf{4}}.


    : Geometric Progression

    The nthn^{th} term of a geometric progression is given by Tn=3×2n−1T_n = 3 \times 2^{n-1}. Find the first term and the common ratio.

  5. Find the first term (T1T_1).

    Substitute n=1n=1 into the formula for the nthn^{th} term.

    T1=3×21−1T_1 = 3 \times 2^{1-1} T1=3×20T_1 = 3 \times 2^0 T1=3×1T_1 = 3 \times 1 T1=3T_1 = 3
  6. Find the second term (T2T_2).

    Substitute n=2n=2 into the formula for the nthn^{th} term.

    T2=3×22−1T_2 = 3 \times 2^{2-1} T2=3×21T_2 = 3 \times 2^1 T2=3×2T_2 = 3 \times 2 T2=6T_2 = 6
  7. Find the common ratio (rr).

    The common ratio is the ratio of any term to its preceding term.

    r=T2T1r = \frac{T_2}{T_1} r=63r = \frac{6}{3} r=2r = 2

    The first term is 3\boxed{\textbf{3}} and the common ratio is 2\boxed{\textbf{2}}.


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