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Higher November 2020 Unit 1 Q1

WJECHigherCurrent spec5 marksSequences

1.

(a) Write an expression for the \(n\)th term of the following sequence. [2]

2     7     12     17     ……………

\(n\)th term = ……………………

(b) The first four diagrams in a sequence are shown below.
Diagrams 1 to 4: triangular arrangements of 1, 3, 6 and 10 circles

Complete the following subtraction. [1]

Box: Number of circles in Diagram 17, minus box: Number of circles in Diagram 16, equals an empty box
(c) The first three diagrams in another sequence are shown below.
Diagrams 1 to 3 made of dots: 4 dots, 6 dots and 8 dots

Give an expression, in terms of \(n\), for the number of dots ( ● ) in Diagram \(n\).
You must simplify your expression. [2]