已知x+y=3,xy=-12,求x²+y²与x²-xy+y²的值._数学解答

已知x+y=3,xy=-12,求x²+y²与x²-xy+y²的值.

人气：132 ℃　时间：2020-03-29 12:14:55

解答

x²+y²
=(x+y)²-2xy
=3²-2*(-12)
=9+24
=33
x²-xy+y²
=x²+2xy+y²-3xy
=(x+y)²-3xy
=3²-3*(-12)
=9+36
=45