a) 5bc - 5c = 5c(b - 1)
b) 5у - 5х + y^{2} - ху = -5(x - y) + (y - 5)(y - 1)
c) y^{2} - 2y + 1 = (y - 1)^{2}
a) 5bc - 5c = 5c(b - 1)
b) 5у - 5х + y^{2} - ху = -5(x - y) + (y - 5)(y - 1)
c) y^{2} - 2y + 1 = (y - 1)^{2}