15.
a) A=(3-1)^2-15+6=4-15+6=> A = - 5
b) -5+5x-10 = 5x-15 = 5(x-3)
c) 2(-5)-4xy-2y^2 = -10 - 4xy -2y^2 = 2(-5-2xy-y^2)
