Have I solved this problem correctly?

\begin{align} \int\limits_{-\infty}^{\infty}\left(t^2-1\right)\delta\left(t\right)\:dt&=\int\limits_{-\infty}^{\infty}t^2\delta\left(t\right)\:dt-\int\limits_{-\infty}^{\infty}\delta\left(t\right)\:dt\tag{1} \\ &=\int\limits_{-\infty}^{\infty}t^2\delta\left(t\right)\:dt-1\tag{2} \\ &=0-1=\boxed{-1.}\tag{3} \end{align}

Such that $\delta\left(t\right)$ is the dirac-delta function.


  • 4
    $\begingroup$ I don't really see the point in splitting up the integral, we can just evaluate $t^2-1$ at $t=0$ directly no? $\endgroup$ – anon Dec 23 '14 at 22:34
  • $\begingroup$ +1 You did fine but you don't need to split the integral as @anon already pointed out. $\endgroup$ – Felix Marin Dec 23 '14 at 23:06

Using the property

$$ \int_{-\infty}^\infty f(t)\delta(t)\, dt = f(0) $$ for $f(t)=t^2-1$ you have $$ \int_{-\infty}^\infty (t^2-1)\delta(t)\, dt = -1. $$


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