计算 当x=0.5 y=2时(3xy-2x^2+0.5y^2)(3xy+2x^2-0.5y^2)的值

问题描述:

计算 当x=0.5 y=2时(3xy-2x^2+0.5y^2)(3xy+2x^2-0.5y^2)的值

(3xy-2x^2+0.5y^2)(3xy+2x^2-0.5y^2)
=(3xy)^2-(2x^2-0.5y^2)^2 代入得:
=3^2-(2*0.5^2-0.5*2^2)^2
=9-(3/2)^2
=27/4