Question

chứng minh:

a) (x-1)(x+1)=x²-1

b) (x+1)(x²-x+1)=x³

c) (x+y)(x+y)=x²+2xy+y²

Answer 1

`a)`\(\left(x-1\right)\left(x+1\right)=x^2+x-x-1=x^2-1\)

`b)`\(\left(x+1\right)\left(x^2-x+1\right)=x^3-x^2+x+x^2-x+1=x^3+1\)

`c)`\(\left(x+y\right)\left(x+y\right)=x^2+xy+xy+y^2=x^2+2xy+y^2\)

Answer 2

a) \(\left(x-1\right)\left(x+1\right)=x^2+x-x-1=x^2-1\)

b) \(\left(x+1\right)\left(x^2-x+1\right)=x^3-x^2+x+x^2-x+1=x^3+1\)

c) \(\left(x+y\right)\left(x+y\right)=x^2+xy+xy+y^2=x^2+2xy+y^2\)