1.7.2 Types of sequence (A-level only)

A sequence $x_1, x_2, x_3, \dots\,$ is defined by

\begin{aligned}x_1 &= a \\x_n &= 3x_{n-1} + 2, \quad n \geq 2\end{aligned}

a.

Find an expression for $x_2\,$ in terms of $a$ .

[1]

b.

Show that $x_3 = 9a + 8$ .

[2]

c.

Find $∑r=14xr\sum_{r=1}^4 x_r$ in terms of $a$ .

[3]

A sequence $x_1, x_2, x_3, \dots\,$ is defined by

\begin{aligned}x_1 &= a \\x_n &= 3x_{n-1} + 2, \quad n \geq 2\end{aligned}

a.

Find an expression for $x_2\,$ in terms of $a$ .

[1]

b.

Show that $x_3 = 9a + 8$ .

[2]

c.

Find $∑r=14xr\sum_{r=1}^4 x_r$ in terms of $a$ .

[3]

1.7.2 Types of sequence (A-level only) Questions