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Problem
Problem
If for a positive integer
n
n
n
, the quadratic equation
x
(
x
+
1
)
+
(
x
+
1
)
(
x
+
2
)
⋯
+
(
x
+
n
−
1
)
(
x
+
n
)
=
10
n
x(x+1) + (x+1)(x+2) \dots + (x+n-1)(x+n) = 10n
x
(
x
+
1
)
+
(
x
+
1
)
(
x
+
2
)
⋯
+
(
x
+
n
−
1
)
(
x
+
n
)
=
10
n
has two consecutive integral solutions, then
n
n
n
is equal to a. 11 b. 12 c. 9 d. 10
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