查人人中国名人网华为正在运行怎么关闭:数学题,,
来源：百度文库 编辑：查人人中国名人网 时间：2024/05/12 06:27:35
how many positive integers n are there such that both n and n+99 are perfect squares?
n=x^2
n+99=y^2
so: y^2-x^2=(y+x)(y-x)=99
for:99=9*11,3*33,1*99
=> x=1,y=10
or x=15,y=18
or x=49,y=50
so: n=x^2=1,225,2401
=> there are 3 those integers