计算(1)解方程组:3x?y=75x+2y=8(2)解方程组:3x?2y=9x+2y=?1(3)化简:12?3×13+8+(π+1)0(4

计算(1)解方程组:3x?y=75x+2y=8(2)解方程组:3x?2y=9x+2y=?1(3)化简:12?3×13+8+(π+1)0(4)6×13?16×18.

(1)
3x?y=7①
5x+2y=8②

①×2得,6x-2y=14③,
②+③得,11x=22,
解得,x=2,
将x=2代入①得,y=3×2-7=-1,
不等式组的解集为
x=2
y=?1


(2)
3x?2y=9①
x+2y=?1②

①+②得,4x=8,x=2;
将x=2代入②得,2y=-1-x=-1-2=-3,
y=-
3
2
,不等式组的解为
x=2
y=?
3
2


(3)
12
?3×
1
3
+
8
+(π+1)0
原式=2
3
-3×
3
3
+2
2
+1
=2
3
-
3
+2
2
+1
=
3
+2
2
+1;

(4)
6
×
1
3
?
16
×
18

=
6
×
3
3
-4×3
2

=
18
3
-12
2

=
3
2
3
-12
2

=
2
-12
2

=-11
2
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