sum b ml.khanna set 46

sum (b)

2 Answers

1/(x²+x+1)

= (x+1)-x
__________

1+x(x+1)

so it gives tan^-1a - tan ^-1b formula...

if u do this for the whole sumation, you will get tan^-1(x+n) - tan^-1 x

now it is one step. :)

EASY!!!

each term within tan inv is of da form : [(x+n) - (x+n-1)]/[1+(x+n)(x+n-1)]
this is telescopic form....

ho gaya naa!!!

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