Help with functions

[Hell0]

y= ±2x+7
y= rad(5-x) (all under the rad)
y= 1/(x+62) - 2
y= -3^x + 41 (no parentheses around the -3 purposely)

how many are functions? this is what i think

no, yes, yes, yes
what do you think and why?

[FWT]

y= ±2x+7
y= rad(5-x) (all under the rad)
y= 1/(x+62) - 2
y= -3^x + 41 (no parentheses around the -3 purposely)

how many are functions? this is what i think

no, yes, yes, yes
what do you think and why?

I agree. Why? Because the last three match the definition of "function" but the first one doesn't.