Question

合并同类项化简先化简,在求值2x^2+(-x^2+3xy+2y^2)-(x^2-xy+2y^2).其中x=1/2008,

Answer 1

2x^2+(-x^2+3xy+2y^2)-(x^2-xy+2y^2)

=(2x^2 - x^2 - x^2) + (3xy - xy) + (2y^2 - 2y^2)

= 2xy

= 2 * (1/2008 * 2008)

= 2*1

= 2