make yourself a T chart - Where x is one column, the function is the middle and Y is the answer when you plug the value for x into the function.
x 3x-4 Y
if x = -1 then 3(-1)-4 = -7
if x = 0 then 3(0)-4 = -4
if x = 1 then 3(1)-4 = -1
if x = 2 then 3(2)-4 = 2
pick your values for X - do the math (in the middle) and get your answer for Y
the point then looks like this (x,y) where "x" is the value you picked and "y" is the answer after you do the math.
I usually try to pick a couple of negative numbers, then zero then some positive numbers so you see a pattern. You want to do this in case it is one of those crazy ones that is always positive. Let me know if this helps.
You can e-mail me directly if you need more help.
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