Question

(3x-y)^2-(2x+y)^2-5x(x-y),其中x=0.2,y=0.01

Answer 1

（1）(3x-y)^2-(2x+y)^2-5x(x-y)

=9x^2+6xy+y^2-4x^2-4xy-y^2-5x^2+5xy

=-5xy

带入x=0.2,y=0.01,得：-0.01

（2）(x^2+2y)(x^2-2y)+4(x^2+y)^2

=x^4-4y^2+4(x^4+2x^2y+y^2)

=x^4+4y^2+4x^4+8x^2y+4y^2

=5*(-2)^4+8*(-2)^2*5

带入x=-2,y=5 ,得：240