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akusaja
  • Member for 10 years, 11 months
  • Last seen more than a week ago
  • Indonesia
100 votes
14 answers
54k views

How to find a general sum formula for the series: 5+55+555+5555+.....?

12 votes
3 answers
2k views

How many pairs of positive integers $(x,y)$ satisfy the equation $x^2 - 10! = y^2$?

7 votes
3 answers
947 views

Is $e^{i+\pi}$ irrational or not?

6 votes
4 answers
245 views

Integer solutions to $a^{2014} +2015\cdot b! = 2014^{2015}$

6 votes
4 answers
4k views

How to find the general formula for this recursive problem?

4 votes
3 answers
228 views

What is the largest possible value from $x_1^{2014}+x_2^{2014}$ from this following problem?

4 votes
4 answers
1k views

How to find the solution of $\sqrt{x^2+12x+35} \geq x-10$?

4 votes
3 answers
563 views

Find all positive integer solutions $(x,y,z)$ that satisfy $5^x \cdot 7^y +4= 3^z$?

4 votes
3 answers
6k views

How many subsets of A={1,2,3,...,10} have the property that the sum of their elements is $\geq 28$?

4 votes
4 answers
804 views

What is $\int\log(\sin x)~dx$?

4 votes
6 answers
171k views

How many even numbers of four digits can be formed with the digits 0,1,2,3,4,5 and 6 no digit being used more?

4 votes
2 answers
123 views

How to prove that the angle between two sides of that triangle is less than 60 degree?

3 votes
2 answers
501 views

How to prove the formula of altitude from this following triangle?

3 votes
2 answers
1k views

Area ratio in triangle?

3 votes
3 answers
206 views

How to find the maximum integer value of n such that 25! > $3^n$

3 votes
1 answer
95 views

What is the solution sets for $(5x-2)^{x-5}=(5x-2)^{2x+1}$?

2 votes
3 answers
16k views

How to derive the volume and surface area formula for truncated cylinder without calculus?

2 votes
1 answer
143 views

How to solve this kind of combinatorics problem?

2 votes
2 answers
2k views

Find the shortest distance between line and plane in this cuboid?

2 votes
1 answer
178 views

How to find the value of this indefinite integral?

2 votes
4 answers
92 views

How to factorize $2x^2-3xy-2y^2+7x+6y-4=0$ without software?

2 votes
2 answers
120 views

General formula of fraction integral

2 votes
1 answer
215 views

How to prove these equations base on this following interior and exterior angle bisectors problem?

2 votes
1 answer
73 views

How to find the multiplication of $pq \times abc$ such that the result is producing the same digits from the original problem?

2 votes
1 answer
979 views

How to find the general sum formula of this logarithmic series $\log 5+\log 5+ \log 605+\log 6655+\dots$

2 votes
0 answers
217 views

Find all pair(s) of positive integer $(a,b)$ such that $\frac{a^2}{2ab^2 -b^3+1}$ is also positive integer too?

2 votes
1 answer
135 views

How to rationalize this root form?

1 vote
5 answers
182 views

How to solve this absolute value equation?

1 vote
1 answer
126 views

How many natural value of n such that $n^5+2n^4+n-1$ is prime number?

1 vote
1 answer
223 views

How can we know that x^x is an exponential function or not without drawing the graphic?