Given f'(x) = 2x^2-5x-7 to find f(x), if  f(0) =
   -3.
First we find the f(x).
Since f'(x)
   is given, f(x) = Int f'(x) dx.
Therefore f(x) = Int (2x^2-5x+7)
   dx.
f(x) = Int 2x^2dx - Int5xdx + Int 7
   dx.
f(x) =  2 (1/3)x^3 - 5(1/2)x^2 +7x +Const , as Int Kx^n dx =
   K(1/n+1)x^(n+1) , for all n except n = -1.
Therefore f(x) =
   (2/3)x^3-(5/2)x^2+7x +C....(1)
Now we use the condition f(0) = -3 to
   find C:
f(0) = (2/3)*0^3-(5/2)*0^2+7*0 +C =
   -3.
Therefore C = -3.
So we rewrite 
   f(x) in (1) replacing C by -3:
f(x) = (2/3)x^3-(5/2)x^2+7x
   -3.
No comments:
Post a Comment