Help with heaviside function

Hi all! Can anyone help me out with turning these equations into

M1= one eq. with heaviside 
M2= one eq. with heaviside 

M1:
0<=x<=10 >    M1 =  20.555*x 150,
10<x<=20 >    M1 =  -0.0167*(x-10)^3 - 0.5*(x-10)^2 + 20.555*x- 150,
20<x<=30 >    M1 =  5.555*x + 83.35,

M2: 
0<=x<=a  >    M2 = (1-a/30)*x,
a<x<=30  >    M2 = a*(1-x/30)

Best, A

[dpb]

Oliver Heaviside was an English self-taught electrical engineer, mathematician, and physicist who adapted complex numbers to the study of electrical circuits and, amongst other innovations, invented the Heaviside step function. (mostly Wikipedia intro...dpb)

Hence, it's "heaviside" w/ an "eye", not "heavy" as in weighty...