a, 100x2 - (x2 +25)2 = (100 + x + 25)(100-x-25)=(x+125)(75-x)
b, phần này đề có nhầm lẫn hem ạ?
c, x4 +3x3 -9x-27 = x3(x+3) - 9(x+3) = (x+3)(x3-9)
d, (x2 +1)2 - 4x2 = (x2+1+2x)(x2+1-2x) = (x+1)2(x-1)2
e, x3 -3x2 +3x-1 -8y3= (x-1)3-(2y)3
= (x-1-2y)[(x-1)2+(x-1).2y+4y2 ]
=(x-1-2y)(x2-2x+1+2xy-3y+4y2 ]
=.= hk tốt!!