已知a2-4a+b2-b/2+65/16=0,则a2-4b=_.

问题描述:

已知a2-4a+b2-

b
2
+
65
16
=0,则a2-4
b
=______.

∵a2-4a+b2-

b
2
+
65
16
=0,
a2-4a+4+b2-
b
2
+
1
16
=0,
(a-2)2+(b-
1
4
2=0,
∴a-2=0,b-
1
4
=0,
∴a=2,b=
1
4

∴a2-4
b
=22-4
1
4
=4-2=2.
故答案为:2.