Question

thực hiện phép tính ( lớp 8)

a) ( 3x+2y)(x^2-3xy+1)

b) (x+3)(x-3)(x+1)

 

Giải chi tiết. cần nhanh.

 

Answer 1

a) \(\left(3x+2y\right)\left(x^2-3xy+1\right)=3x^3-9x^2+3x+2yx^2-6xy^2+2y\)

b) (x+3)(x-3)(x+1)=(x²-9)(x+1)=x³-9x+x²-9

Answer 2

a) \(\left(3x+2y\right)\left(x^2-3xy+1\right)\)

\(=\left(3x+2y\right)x^2-\left(3x+2y\right)\cdot3xy+\left(3x+2y\right)\cdot1\)

\(=3x^3+2x^2y-9x^2y-6xy^2+3x+2y\)

b) \(\left(x+3\right)\left(x-3\right)\left(x+1\right)\)

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

\(=\left(x^2-9\right)x+\left(x^2-9\right)\cdot1\)

\(=x^3-9x+x^2-9\)