题目内容

(1)计算:(-1)2012-|1-6tan30°|-(-
5
)0+
12

(2)解方程组:
2x-y=-5…①
3x+2y=-4…②

(3)先化简,再求值:
x-y
x+3y
÷
x2-y2
x2+6xy+9y2
-
3y
x+y
,其中x=-
1
2
,y=-1.
(1)(-1)2012-|1-6tan30°|-(-
5
)0+
12

=1-(2
3
-1)-1+2
3

=1;

(2)
2x-y=-5…①
3x+2y=-4…②

由①×2得:4x-2y=-10,③,
③+②得:7x=-14,
x=-2,
把x=-2代入①得:y=1,
所以方程组的解是
x=-2
y=1


(3)
x-y
x+3y
÷
x2-y2
x2+6xy+9y2
-
3y
x+y

=
x-y
x+3y
×
(x+3y)2
(x+y)(x-y)
-
3y
x+y

=
x+3y
x+y
-
3y
x+y

=
x
x+y

x=-
1
2
,y=-1代入上式得:
-
1
2
-
1
2
-1
=
1
3
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