Question

Tính (2x-3y) (2x+3y)

 

Answer 1

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

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

\(=2x.2x+2x.3y-3y.2x-3y.3y\)

\(=4x^2+6xy-6xy-9y^2\)

\(=4x^2+\left(6xy-6xy\right)-9y^2\)

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

Answer 2

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

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

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