f ( x ) = x^3
( x | f ( x ) )
2.Punkt
( x + h | f ( x + h ) )
( f ( x + h ) - f ( x ) ) / ( x + h - x )
( ( x + h ) ^3 - x^3 ) / h
[ ( x^2 + 2xh + h^2 ) * ( x + h ) - x^3 ] / h
( x^3 + 2x^2h + xh^2 + x^2h+ 2xh^2 + h^3 - x^3 ) / h
( 2x^2h + xh^2 + x^2h + 2xh^2 + h^3 ) / h
h * ( 2x^2 + xh + x^2 + 2xh + h ) / h
lim h -> 0 [ 2x^2 + xh + x^2 + 2xh + h ] = 3x^2
f ´( x ) = 3 * x^2