Question

find derivative of x^3+4x-2 using the def. of a derivative. Pleasee help

Answer 1

dy/ dx = lim h -> 0 [(x+h)^3 + 4(x+h) -2 - (x^3 +4x -2)]/h

Answer 2

so divide all of it by h?

Answer 3

yes..now expand everything and get the final expression and divide everything by h and then put h=0

Answer 4

ok thanks. do you know the answer if i do it on my own and ask you if it's right?

Answer 5

yeah tell me wt u got

Answer 6

okk hold on

Answer 7

is it 6x-4?

Answer 8

nope..try again

Answer 9

3x^2+4x?

Answer 10

3x^2 + 4

Answer 11

(x^3 - h^3 -3x^2h + 3xh^2 + 4x -4h +2 - x^3 -4x -2) / -h
(-h^2 -3x^2 +3xh -4 )/-1
3x^2 + 4

Answer 12

divide by -h not h

Answer 13

why?

Answer 14

bcoz i used f(x-h) - f(x)

Answer 15

if i would ve used f(x+h) - f(x) wed hv used h