Question

Bài 3: Tính

a) ( x - 2y )²

b) ( 2x² + 3 )²

Answer 1

\(a,=x^2-2.x.2y+4y^2\\ =x^2-4xy+4y^2\\ b,=4x^4+2.2x^2.3+9\\ =4x^4+12x^2+9\)

Answer 2

\(a,=x^2-2\cdot x\cdot2y+\left(2y\right)^2=x^2-4xy+4y^2\\ b,=\left(2x^2\right)^2+2\cdot2x^2\cdot3+3^2=4x^4+12x^2+9\)