Show that the three LTI systems with impulse responses h$1($t$)=$ u$($t$),$ hz$($t$)=-2$o$($t$)+5$e$-21$ u$($t$),$ and all have the same response to x$($t$)=$ cost$.($b$)$ Find the impulse response of another LTI system with the same response to cost$.$ This problem illustrates the fact that the response to cos t cannot be used to specify an LTI system uniquely