Question

rút gọn các biểu thức:

a, (2x+3)² - (2x-3)²

b, (x-2y)³ + (x+2y)³

c, (2x+3)(3-2x) + 4x² 

mình cần gấp trong sáng mai ạ

 

Answer 1

a.

\(\left(2x+3\right)^2-\left(2x-3\right)^2=\left(2x+3+2x-3\right)\left(2x+3-2x+3\right)=24x\)

b.

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

\(=\left(2x\right)^3-3\left(x^2-4y^2\right).2x=8x^3-6x^3+24xy^2=2x^3+24xy^2\)

c.

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

\(=9-4x^2+4x^2=9\)