if you get 0 when you set y to 0 does that indicate a turning point, or just not a max/min point ? this is 'setting y'=0' i mean i have a function, and am meant to find the max or min so i get the derivative of that right? to find slope... and so i set say y'=3x+4 to 0 so 0=3x+4 IF that comes out as zero = zero (i know this one wont) does that mean i have a turning point or just that i've done the quesiton wrong or something else?

That just means your potential max/min is at zero. You won't get a 0=0 You'll get x=0 or something similar unless its like y'=3. That is never zero.

extrema HAVE zero values for slope; but there are instances where an inflection can also have 0 zlope

Exactly. In general. y'=0 does NOT imply that y''=0.

but if your derivative is a linear; that means it came from a quadratic; and they have no inflections

0=3x+4 when x = -4/3 <.........(-4/3)...........> - + this goes from - to + slopes which means you have a minimum

ok

yay i can reply

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