a) x 2 – x – 12 b) x 3 – 64.
c) m 3 n 3 – m 2 n + 5 mn 2 – 5 d) 16 x 4 – 1.
giải
a) (x+3)(x-4)=\(x^2\) -4x+3x-12
=\(x^2\) +(-4x+3x)-12
=\(x^2\) -x-12
b) (x-4)(\(x^2\) +4x+16)=\(x^3\) +\(4x^2\) +16x-\(4x^2\) -16x-64
=\(x^3\) +(\(4x^2\) -\(4x^2\) )+(16x-16x)-64
=\(x^3\) -64