\(f(x) = (x^2 + 6x + 9)^{50} - 4x + 3 = (x + 3)^{100} - 4x + 3\)
Substituting \(r_1, r_2,\cdots,r_{100}\) into f(x) = 0, we have
\(\begin{cases}\left(r_1 + 3\right)^{100} - 4r_1 + 3 = 0\\\left(r_2 + 3\right)^{100} - 4r_2 + 3 = 0\\\cdots\\\left(r_{100} + 3\right)^{100} - 4r_{100} + 3 = 0\end{cases}\)
Moving all the terms to the right hand side and adding them up,
\((r_1 + 3)^{100} + (r_2 + 3)^{100} + \cdots + (r_{100} + 3)^{100} = 4(r_1 + r_2 + \cdots + r_{100}) - 300\)
That means the required answer is 4(sum of roots) - 300.
By Vieta's formula, \(\text{sum of roots} = -\dfrac{\text{coefficient of }x^{99}}{\text{coefficient of }x^{100}}\).
Using binomial theorem, the coefficient of x100 is 1 and the coefficient of x99 is 300.
Therefore \(r_1 + r_2 + \cdots + r_{100} = -300\).
Therefore \((r_1 + 3)^{100} + (r_2 + 3)^{100} + \cdots + (r_{100} + 3)^{100} = 4(-300) - 300 = \boxed{-1500}\)
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