Respuesta :

Answer:

4x

Step-by-step explanation:


lim  2(x+h)^2 +4 - (2x^2 +4)

   -------------------------------------

             h

FOIL the (x+h)^2   x^2 +xh+xh+h^2  = x^2 +2xh+h^2  and substitute in

lim  2(x^2 +2xh +h^2) +4 - (x^2 +4)

   -------------------------------------

             h

Distribute the 2 and the negative sign

lim  2x^2 +4xh +2h^2 +4 - 2x^2 -4

   -------------------------------------

             h

Combine like terms (the 2x^2 and the 4 go away)

lim   +4xh +2h^2

   -------------------------------------

             h

Factor out an h from the numerator

lim   h(4x +2h)

   -------------------------------------

             h

Cancel the h from the top and bottom

lim   +4x +2h

  The limit as h goes to 0, means we let h be 0

lim  4x +0


lim is 4x

Aha here is a trick. If you notice, this is the derivative of 2x^2+4. You can use the definition of the derivative to check it. The derivative of 2x^2 + 4, well the 4 goes away and the x^2 becomes 2x, times two which os 4x.
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