计算:1/3+6+1/3+6+9+1/3+6+9+12+…+1/3+6+9+12+…+150= _ .
问题描述:
计算:
+1 3+6
+1 3+6+9
+…+1 3+6+9+12
= ___ . 1 3+6+9+12+…+150
答
+1 3+6
+1 3+6+9
+…+1 3+6+9+12
,1 3+6+9+12+…+150
=
×(1 3
+1 1+2
+1 1+2+3
…+1 1+2+3+4
),1 1+2+3+4+…+50
=
×[1 3
+2 2×(2+1)
+2 3×(3+1)
…+2 4×(4+1)
],2 50×(50+1)
=
×[2 3
-1 2
+1 3
-1 3
+1 4
-1 4
…+1 5
-1 50
],1 51
=
×[2 3
-1 2
],1 51
=
×2 3
,49 102
=
49 153