Question

数学题三道计算(X-2Y+Z)(X+2Y-Z)[(1/4)X-(2/5)Y]^2*[(1/4)X+(2/5)Y]^2[(

Answer 1

(1):(x-2y+z)(x+2y-z)=[x-(2y-z)][x+(2y-z)]=x^2-(2y-z)^2=x^2-4y^2-z^2+4yz;(2):(x/4-2y/5)^2(x/4+2y/5)^2=[(x/4-2y/5)(x/4+2y/5)]^2=(x^2/16-4y^2/25)^2=x^4/256-xy/50+16y^4/625;(3):[(2t+1)^2-(1-2t)^2](t^2-2)=[(2t+1)+(1-2t)][(2t+1)-(1-2t)](t^2-2)=2*4t(t^2-2)=8t^3-16t