If f(a)=f(b)=0 then there is at least one a<c<b such that f'(c)=0
The Attempt at a Solution
How do i know y' isn't 0 somewhere? if it's continuously descending, so i make y''=12x-6. it's a straight line, so there are no twist points in y'.
But to know y'' doesn't equal 0 somewhere i take y'''=12
Do i really need to reach y''' in order to answer the question? i think i exaggerate
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