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.
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