Form 1 Maths

In each of the following sequences, find the next 3 terms.
1b. 1,-4,9, -16,25
1d. 18,13,8,3
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The following figures are formed by equilateral triangles.
1st Figure=1 triangle
2nd Figure=4 triangles
3rd Figure=9 triangles
3a. Let x be the number of equilateral triangles in each figure and S be the perimeter. Complete the following table.
a th Figure a=1 a=2 a=3
Number of triangles x ? ??
Perimeter S ? ? ?
3b. Express x and S in terms of a.
3c. Find the values x and S when a=10 and a=100.