Question

bài 1 : tính

a) (5-xy)²

b) (3-2y)²

c) (3+x²) . (3-x²)

d) (5x-2y).( 25x²+10xy+4y²)

e) (3x+y). (9x²-3xy+y²)

g) (2x-1)³

bài 2 : viết các biểu thức sau về dạng tích

a) x²-2x+1

b) 4x²+12x+9

c) x³-27

d) 8x³+1

e) 4x²-1

g) x³-9x²+27x-27

h) x³+6x²+12x+8

bài 3 : rút gọn

a) ( x+3)²-(x-1)²

b) (3x+2).(3x-2)-9.(x+2).(x-2)

c) (x-3).(x²+3x+9)-(x³-5)

d) (x+1)³-x²(x+2)

e) (4x+y).(16x²-4xy+y²)-(4x-y).(16x²+4xy+y²)

Answer 1

\(\left(5-xy\right)^2=25-10xy+x^2y^2\)

\(\left(3-2y\right)^2=9-12y+4y^2\)

\(\left(3+x^2\right)\left(3-x^2\right)=9-x^4\)

\(\left(5x-2y\right)\left(25x+10xy+4y^2\right)=\left(5x-2y\right)\left(5x+2y\right)=25x^2-4y^2\)\(\left(3x+y\right)\left(9x^2-3xy+y^2\right)=\left(3x+y\right)\left(3x-y\right)=9x^2-y^2\)