Khai triển: a) (3x + 1)^2 ; b) (2y + 3x)^2; c) (2x – 3)^2;
Khai triển:
a) (3x + 1)2 ;
b) (2y + 3x)2;
c) (2x – 3)2;
c) (2x – 3)2 = (2x)2 ‒ 2.2x.3 + 32 = 4x2 – 12x + 9.