①x+y=2
xy=-1
即2x-x^2+1=0
x^2-2x-1=0
解得：x = 1 + √2 或 x = 1 - √2
所以有两种情况
x = 1 + √2
y=1- √2
或
x = 1 - √2
y=1+√2
② 设长为a 宽为5-a ,则：
5a-a^2=6
a^2-5a+6=0
且a>5-a
a^2-5a+6.25=0.25
(a-2.5)^2 =0.5^2
即a-2.5= 0.5 或a-2.5=-0.5
解得a=3 或a=2(a
①x+y=2
xy=-1
即2x-x^2+1=0
x^2-2x-1=0
解得：x = 1 + √2 或 x = 1 - √2
所以有两种情况
x = 1 + √2
y=1- √2
或
x = 1 - √2
y=1+√2
② 设长为a 宽为5-a ,则：
5a-a^2=6
a^2-5a+6=0
且a>5-a
a^2-5a+6.25=0.25
(a-2.5)^2 =0.5^2
即a-2.5= 0.5 或a-2.5=-0.5
解得a=3 或a=2(a