2004×2002/2003; (1/15+2/17)×15×17; 1/1×2+1/2×3+1/3×4+…+1/99×100.

问题描述:


2004×
2002
2003
;            
1
15
+
2
17
)×15×17;                   
1
1×2
+
1
2×3
+
1
3×4
+…+
1
99×100

(1)2004×

2002
2003

=(2003+1)×
2002
2003

=2003×
2002
2003
+1×
2002
2003

=2002+
2002
2003

=2002
2002
2003

(2)(
1
15
+
2
17
)×15×17  
=(
1
15
+
2
17
)×(15×17)
=
1
15
×15×17+
2
17
×17×15
=17+30
=47;
(3)
1
1×2
+
1
2×3
+
1
3×4
+…+
1
99×100

=1-
1
2
+
1
2
-
1
3
+
1
3
-
1
4
+…+
1
99
-
1
100

=1-
1
100

=
99
100