Find the sum of the first 18 terms of the progression 3, 6, 12......

At what value of x is the function x\(^2\) + x + 1 minimum?

The angle of a sector of s circle, radius 10.5cm, is 48°, Calculate the perimeter of the sector

Find the length of a side of a rhombus whose diagonals are 6cm and 8cm

Each of the interior angles of a regular polygon is 140°. How many sides has the polygon?