Question

CMR:

A=(x+2)(x-3)-(x-2)(x+3) chẵn

Answer 1

\(A=(x+2)(x-3)-(x-2)(x+3)\)

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

\(=x^2-3x+2x-6-x^2+2x-3x+6\)

\(=\left(x^2-x^2\right)-\left(3x+3x\right)+\left(2x+2x\right)+\left(6-6\right)\)

\(=-2x⋮2\forall x\) Hay A chẵn

Answer 2

\(A=(x+2)(x-3)-(x-2)(x+3)\)

\(A=x(x-3)+2(x-3)-x(x+3)+2(x+3)\)

\(A=x^2-3x+2x-6-x^2-3x+2x+6\)

\(A=(x^2-x^2)-(3x+3x)+(2x+2x)-(6+6)\)

\(A=-6x+4x\)

\(A=-2x\)

\(\Leftrightarrow A\)chẵn