Dat moet kunnen...

$\eqalign{ & f(x) = ax^2 + bx + c \cr & I. \cr & A:f(m) = am^2 + bm + c \cr & B:f(n) = an^2 + bn + c \cr & rico_{AB} = \frac{{am^2 + bm + c - \left( {an^2 + bn + c} \right)}} {{m - n}} \cr & rico_{AB} = \frac{{am^2 + bm + c - an^2 - bn - c}} {{m - n}} \cr & rico_{AB} = \frac{{a(m^2 - n^2 ) + b(m - n)}} {{m - n}} \cr & rico_{AB} = a\left( {m + n} \right) + b \cr & II. \cr & f'(x) = 2ax + b \cr & C:f'\left( {\frac{{m + n}} {2}} \right) = 2a \cdot \frac{{m + n}} {2} + b \cr & C:f'\left( {\frac{{m + n}} {2}} \right) = a\left( {m + n} \right) + b \cr}$

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