c) 2x2 + 10x + 8
= 2x2 + 2x + 8x + 8
= 2x( x + 1) + 8(x + 1)
= 2(x + 1)(x + 4)
d) x2 - 7xy + 10y2
= x2 - 2xy - 5xy + 10y2
= x(x - 2y) - 5y(x - 2y)
= (x - 2y)(x - 5y)
e) x4 + 4x2 - 5
= x4 - x2 + 5x2 - 5
= x2(x2 - 1) + 5(x2 - 1)
= (x - 1)(x + 1)(x2 + 5)
f) x3 - 7x - 6
= x3 - x - 6x - 6
= x(x2 - 1) - 6(x + 1)
= x(x - 1)(x + 1) - 6(x + 1)
= (x + 1)(x - 1)(x - 6)
pn coi kt lại nhé