Решите (у-3)^2 4х^2 -81 25х^2-30ху+9у^2

(y-3)ˇ2 = yˇ2 -6y +9 4xˇ2 -81=(2x)ˇ2 - 9ˇ2 = (2x+9)(2x-9) 25xˇ2 -30xy+9yˇ2 = (5x)ˇ2 - 2.5.3xy +(3y)ˇ2=(5x-3y)ˇ2