Please help me thank you sm if u did Find the value (1/1) + (1/1+2) + (1/1+2+3) + … + (1/1+2+3+…+2021) =? [Hint: a_k = (1/1+2+3+…+k) ]​

The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm