4. Fatore as expressões. a) 4x4y2 –6x3y3 +8x2y4 = b) 18ab3c² +27a3b4c3 -9a2b5c4 -45a2b3c2 = c) a2+3ab-2ac-6bc= d) x3–3x2y2 +6y3 – 2xy = e) x2 +z+x3y+xyz=zx2 -z2 = f) a4b6-9c2 = g) 9a4-b4 = h) 25x6 + 10x3y+y2 = i) 49x4 +14x2 +1= j) 20a2b2 – 2a4 – 50b4 =