Question

已知x+y=1,xy=-6,求下列式子的值

Answer 1

x²+y²

=x²+2xy+y²-2xy

=(x+y)²-2xy

=1+12

=13

（x+1）（y+1）（x-1）（y-1）

=(x+i)(x-1)(y+1)(y-1)

=(x²-1)(y²-1)

=x²y²-x²-y²+1

=x²y²-(x²+y²)+1

=36-13+1

=24