有3條數唔識計

1.我估你抄錯題目,最尾個個我估係15n^2
14m^2-10mn-21mn+15n^2
=2m(7m-5n)-3n(7m-5n)
=(7m-5n)(2m-3n)

2.2x^3-3y+2x-3x^2y
=2x^3+2x-3y-3x^2y
=2x(x^2+1)-3y(x^2+1)
=(x^2+1)(2x-3y)

3. ax^2 -2x^2b^2 -2b^2y^2 +ay^2 [你第2項應該漏左個2次方]
=ax^2+ay^2-2x^2b^2-2b^2y^2
=a(x^2+y^2)-2b^2(x^2+y^2)
=(x^2+y^2)(a-2b^2)