问题 解答题
计算:(1)
2
(2cos45°-1)+(4-5π)0-(
2
-1)-1

(2)先化简,再求值.
x-5
x2-9
÷
x2-2x-15
x2+6x+9
+
1
x-3
,其中x=
3
+2
答案

(1)原式=

2
(2×
2
2
-1)+1-
1
2
-1

=

2
2
-1)+1-
2
-1

=2-

2
+1-
2
-1

=2-2

2

(2)原式=

x-5
(x+3)(x-3)
×
(x+3)2
(x+3)(x-5)
+
1
x-3

=

1
x-3
+
1
x-3

=

2
x-3

∵x=

3
+2,

∴原式=

2
x-3
=
2
3
+2-3
=
2
3
-1
=
3
+1

多项选择题
多项选择题