9–11 Find the Laplace transforms of the following waveforms and plot their pole-zero diagrams. Then use MATLAB to validate your results.

(a) f1ðtÞ = 15e−5t −20e−10t  

u t ð Þ

(b) f2ðtÞ = 10 ½cos 1000t + cos 2000t uðtÞ