根号5x+2y=4,根号5x-2y=2,
则
5x+2y=16.(1)
5x-2y=4.(2)
(1)+(2),得
10x=20
x=2
(1)-(2),得
4y=12
y=3
所以
x²-y²
=2²-3²
=4-9
=-5
若x为一个二位整数,则根号x的取值范围是(3