Write an explicit formula for arithmetic sequence whose common difference is -4.5

Solve the equation using the given values: x= -2.5; y= -7.51. 2xy + 2x²

Adrawer contains 12 identical white socks, 18 identical black socks and 14 identical brown socks. what is the least number of socks you must choose, without looking, to be certain that you have chosen two socks of the same colour?

Prove that quadrilateral is a rhombus.