Đáp án:
Giải thích các bước giải:
Bài 1
a) (3-xy²)²-(2-xy²)²
=(3-xy²-2+xy²).(3-xy²+2-xy²)
=5-2xy²
b) 9x²-(3x-4)²
=(3x-3x+4).(3x+3x-4)
=4(6x-4)
c)(a-b²)(a-b²)=(a-b²)²
d) (a²+2a+3)(a²-2a+3)
=a^4+2a³-3a²-2a³-4a²+6a+3a²+6a+9
=a^4-4a²+12a+9
e) (2y-3)
³=(2y)³-3.(2y)².3+3.2y.3²-3³
=8y³-18y²+54y-27
f) (2+x)³
=8+12x+6x²+x³
g) (x-3)³+(2-x)³
=(x-3+2-x)[(x-3)²-(x-3)(2-x)+(2-x)²
= -1(x²-6x+9-2x+x²+6-3x+4-4x+x²)
= -1(3x²-15x+19)
= -3x²+15x-19
h) (x+1)²-(x-1)²+3x²-3x(x-1)(x+1)
=(x+1-x+1)(x+1+x-1)+3x²-3x(x²-1)
=2.2x+3x²-3x³+3x=-3x³+3x²+7x
