Question

if a function is linear does that make it positive?

Answer 1

If you mean the y values, then no it doesn't mean it's always positive.

Consider something like y = 3x+2 which is a linear function. It graphs a straight line through the two points (0,2) and (1,5)

If you plugged a number like x = -10, then...

y = 3x+2

y = 3*(-10)+2

y = -30 + 2

y = -28

So we see that y isn't positive here.