Question

(x的平方+2分之一xy+2分之一y方)- (x方+2分之3xy-2y方)化简 在求出x=- 4分之一 y=2分之一的值

Answer 1

(x^2+1/2xy+1/2y^2)- (x^2+3/2xy-2y^2)

=x^2+1/2xy+1/2y^2- x^2-3/2xy+2y^2

=-xy+5/2y^2

=-(-1/4)×1/2+5/2×（1/2）^2

=1/8+5/8

=3/4