试说明不论x 取何值时,代数式(x+3)^2+(x-3)^2-2(x+3)(x-3)恒为定值

问题描述:

试说明不论x 取何值时,代数式(x+3)^2+(x-3)^2-2(x+3)(x-3)恒为定值

(x+3)^2+(x-3)^2-2(x+3)(x-3)
=x²+6x+9+x²-6x+9-2(x²-9)
=36

不论x 取何值时,代数式(x+3)^2+(x-3)^2-2(x+3)(x-3)恒为定值