a) (a + b)2 – m2 + a + b – m = (a + b + m)(a + b – m) + (a + b – m)
= (a + b – m)(a + b + m + 1)
b) x3 + 6x2 + 12x – 8 = (x – 2)3
Cách khác: x3 + 6x2 + 12x – 8 = (x3 – 8) - 6x2 + 12x
= (x – 2)(x2 + 2x + 2) + 6x(x – 2) = (x – 2)( x2 + 2x + 2 – 6x) = (x – 2)3
c) x2 – 7xy + 10y2 = x2 – 2xy – 5xy + 10y2 = x(x – 2y) – 5y(x – 2y)
= (x – 2y)(x – 5y)
d) x4 + 2x3 - 4x – 4 = (x4 – 4) + (2x3 – 4x) = (x2 – 2)(x2 + 2) + 2x(x2 – 2)
= (x2 – 2)(x2 + 2 + 2x) = (x - √2)( x + √2)( x2 + 2 + 2x)
học tốt
a,(a+b+m)(a+b-m)+(a+b-m)
=(a+b-m)(a+b+m+1)
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hc tốt