The first four terms in a sequence of numbers are given below. T1=(1×3)+8=11T_1 = (1\times 3) + 8 = 11 T2=(2×4)+12=20T_2 = (2\times 4) + 12 = 20 T3=(3×5)+16=31T_3 = (3\times 5) + 16 = 31 T4=(4×6)+20=44T_4 = (4\times 6) + 20 = 44

  1. ((a))

    Find T5T_5.

    Answer ___

  2. ((b))

    Show that the nthn^{\text{th}} term of the sequence, TnT_n, is given by n2+6n+4n^2 + 6n + 4.

  3. ((c))

    Tp−1T_{p-1} and TpT_p are consecutive terms in the sequence.

    Find and simplify an expression, in terms of pp, for the sum of Tp−1T_{p-1} and TpT_p.

    Answer ___

  4. ((d))

    Find the value of pp when the sum of Tp−1T_{p-1} and TpT_p is 303.

    Answer p= ___

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Worked solution

8((a))

1. Use the observed pattern to form and calculate the fifth term

From the pattern,

T5=(5×7)+24T_5 = (5\times 7)+24

=35+24=35+24

=59=59

Answer

T5=59T_5 = 59

8((b))

1. Express the observed pattern for the $n^{\text{th}}$ term

From the given terms,
T1=(1×3)+8=(1)(1+2)+4(1+1)T_1=(1\times3)+8=(1)(1+2)+4(1+1)
T2=(2×4)+12=(2)(2+2)+4(2+1)T_2=(2\times4)+12=(2)(2+2)+4(2+1)
T3=(3×5)+16=(3)(3+2)+4(3+1)T_3=(3\times5)+16=(3)(3+2)+4(3+1)
So, in general,
Tn=n(n+2)+4(n+1).T_n=n(n+2)+4(n+1).

2. Expand and simplify the expression to show the required form

Tn=n(n+2)+4(n+1)T_n=n(n+2)+4(n+1)
=n2+2n+4n+4=n^2+2n+4n+4
=n2+6n+4=n^2+6n+4

Answer

Tn=(n)(n+2)+4(n+2)=n2+6n+4T_n=(n)(n+2)+4(n+2)=n^2+6n+4
Hence, the nthn^{\text{th}} term is n2+6n+4n^2+6n+4.

8((c))

1. Find an expression for $T_{p-1}$ using the nth term formula

From part (b),
Tn=n2+6n+4T_n=n^2+6n+4
Substitute n=p−1n=p-1:
Tp−1=(p−1)2+6(p−1)+4T_{p-1}=(p-1)^2+6(p-1)+4
=p2−2p+1+6p−6+4=p^2-2p+1+6p-6+4
=p2+4p−1=p^2+4p-1

2. Find an expression for $T_p$ using the nth term formula

Substitute n=pn=p:
Tp=p2+6p+4T_p=p^2+6p+4

3. Add the two consecutive terms and simplify

Tp−1+Tp=(p2+4p−1)+(p2+6p+4)T_{p-1}+T_p=(p^2+4p-1)+(p^2+6p+4)
=2p2+10p+3=2p^2+10p+3

Answer

2p2+10p−12p^2+10p-1

8((d))

1. Form a quadratic equation using the sum from part (c)

From part (c),
Tp−1+Tp=2p2+10p−1.T_{p-1}+T_p=2p^2+10p-1.
Given that the sum is 303303,
2p2+10p−1=3032p^2+10p-1=303
2p2+10p−304=02p^2+10p-304=0
p2+5p−152=0p^2+5p-152=0

2. Solve the quadratic equation and select the valid value of $p$

p2+5p−152=0p^2+5p-152=0
(p+16)(p−11)=0(p+16)(p-11)=0
So,
p=−16orp=11.p=-16 \quad \text{or} \quad p=11.
Since pp is a term number, pp must be positive.
p=11p=11

Answer

p=10p=10

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