Question

Thực hiện phép tính:
 

(5 + 3x)^3

(x + 2y + z)(x +2y -z)

 

Answer 1

\(\left(5+3x\right)^3=5^3+3.5^2.3x+5.5.\left(3x\right)^2+\left(3x\right)^3\\ =125+225x+225x^2+27x^3\\ ---\\ \left(x+2y+z\right)\left(x+2y-z\right)\\ =\left(x+2y\right)^2-z^2\\ =x^2+4xy+4y^2-z^2\)

Answer 2

\(\left(5+3x\right)^3\\ =125+3\cdot25\cdot3x+3\cdot5\cdot9x^2+27x^3\\ =27x^3+135x^2+225x+125\)

 

\(\left(x+2y+z\right)\left(x+2y-z\right)\\ =\left(x+2y\right)^2-z^2\\ =x^2+4y^2-z^2+4xy\)