Tính: a) (x – 2y)^2; b) (2x^2 + 3)^2; c) (x – 2)(x^2 + 2x + 4); d) (2x – 1)^3.
Tính:
a) (x – 2y)2;
b) (2x2 + 3)2;
c) (x – 2)(x2 + 2x + 4);
d) (2x – 1)3.
a) (x – 2y)2
= x2 – 2 . x . 2y + (2y)2
= x2 – 4xy + 4y2
b) (2x2 + 3)2
= (2x2)2 + 2 . 2x2 . 3 + 32
= 4x4 + 12x2 + 9
c) (x – 2)(x2 + 2x + 4)
= (x – 2)(x2 + 2 . x + 22)
= x3 – 23
= x3 – 8
d) (2x – 1)3
= (2x)3 + 3 . 2x . 12 – 3 . (2x)2 . 1 – 13
= 8x3 + 6x – 12x2 – 1.