Đáp án:
a) M = (2x + y)² – (y – 2x)²
= 4x² + 4xy + y² – y² + 4xy – 4x²
= 8xy
b) N = (3x + 2)² + 2(2 + 3x)(1 – 2y) + (2y – 1)²
= (3x + 2)² – 2(3x + 2)(2y – 1) + (2y – 1)²
= [(3x + 2) – (2y – 1)]²
= (3x + 2 – 2y + 1)²
= (3x – 2y + 3)²
c) P = (x² + 2xy)² + 2(x² + 2xy).y² + y⁴
= (x² + 2xy + y²)²
= (x² + xy + xy + y²)²
= [x(x + y) + y(x + y)]²
= [(x + y)(x + y)]²
=(x + y)⁴