若x+y=10,xy=24,求x^2-y^2的值
问题描述：
若x+y=10,xy=24,求x^2-y^2的值
答
x^2-y^2=(x+y)(x-y)
(x-y)^2
=(x+y)^2-4xy
=100-96
=4
x-y=-2或2
x^2-y^2
=(x+y)(x-y)
=10×(±2)
=-20或20