4000/sqrt(X^6+100) sqrt= square root right?
4000/(X^6+100)^.5 put it into simpler terms
(X^6+100)^.5 (0)-2000(X^6+100)^-.5 now use the quotient rule
____________________________ <---- division line
[(X^6+100)^.5]^2
Then you just solve the equation, remembering that a ^-N means you have to move it to the denominator. if this is not enough comment and ill solve full thing, but this is how you do it (i think).