Question

1,已知x^2+y^2=2,x+y=1,则xy的值为多少?2,（-3）的m次方+3乘以（-3）的m-1次方的值是多少?

Answer 1

1:

(x+y)^2=x^2+y^2+2xy,带入条件,1^2=2+2xy,所以xy=-1/2

2:

(-3)^m+3*(-3)^(m-1)=(-3)^m-(-3)*(-3)^(m-1)=(-3)^m-(-3)^m=0