is y(t) = 3 f(t-2) +4 a linear, time-invariant (LTI) system?

[magnumtrooper]

i wasn't sure where to post this question (i hope this is right)

i just had a pop quiz in one of my classes, i am wondering if i got the answers correct (the solution hasn't been posted online yet).

y(t) is the output
f(t) is the input

y(t) = 3 f(t-2) +4

is the system linear?

Is the system time invariant?

Although it wasn't asked i was also curious what the answer would be if
"y(t) is the input
f(t) is the output"

thanks!

 

[stapel]

y(t) is the output
f(t) is the input

y(t) = 3 f(t-2) +4

is the system linear?

Is the system time invariant?

What was "f(t)"?

i just had a pop quiz in one of my classes, i am wondering if i got the answers correct (the solution hasn't been posted online yet).

You plugged into the definitions and... then what? What were your steps and reasoning? What were your answers?

Although it wasn't asked i was also curious what the answer would be if
"y(t) is the input
f(t) is the output"

So f(t) = (1/3)(y(t) - 4)? What are your steps and reasoning? What are your answers?

Please be complete. Thank you!

 

[magnumtrooper]

they where not stated.

here is a homework problem we were assigned:
" For the systems described by the following equations, with the input x (t) and output y(t), determine which are time varying and which systems are time invariant:
a. y(t)= x(t-2)
b.y(t)= x(-t)
..."

they are just arbitrary, "some function f(t)". I'm not sure what sort of assumptions we make about the arbitrary function such as assuming where the function exists, that the answers are real numbers, etc.

the math for this class seems simple but understanding the concepts seem hard to comprehend...
like it is hard to visualize the problems graphically and such