Given (1-2x + 5x2- 10x3)(1 +x)n = 1 + a1x + a2x +.......
And that a12 = 2a2
Then the value of n is?
Is it a2x2 that is written as a2x?
Good question, Where did you get it from?
The Answer is 6
By giving out solutions, I will be defeating the whole perpose, and this is not a problem which requires a solution to understand, so I will give a hint, so you can experience the joy of "Getting It" for yourself, if you still don't get it, just reply and i'll give the solution.
Hint : Write the nth term of
and calculate coeffiecients of x and 
by multiplying with the other polynomial, then equate the conditions given
The Answer is 6
By giving out solutions, I will be defeating the whole perpose, and this is not a problem which requires a solution to understand, so I will give a hint, so you can experience the joy of "Getting It" for yourself, if you still don't get it, just reply and i'll give the solution.
Hint : Write the nth term of
and calculate coeffiecients of x and by multiplying with the other polynomial, then equate the conditions given