How is Z transform conversion to step function h[n] ?

i have this equential in matlab : Transfer function: z^2/ z^2 + 0.25 z - 0.125 how will i find h[n]=(0.25)^nu[n]+(0.5)^nu[n] in matlab ?which code must i use ? thank you

[Azzi Abdelmalek]

Ismail, this is a homework http://www.mathworks.com/matlabcentral/answers/55210-discrete-system-solving-with-matlab. You have to post what you've done to get some help

[Sara Hafeez]

define this using tf the way this has been done in the previous post and try.