Question

若x+y=10,xy=24,求x^2-y^2的值

Answer 1

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