X 2 9 90 July 8, 2019 16 32 64 128 5 x 9 2 90 900 x 2 9 2 10 x 1 9 2 90 Feltrinelli 2 x 9 90 X 9 2 x 3x 20 )= 90 2x 9 9 x 8 = 9 x^2
