Question

Find the deriviative of
y=x^2 - 3x - 1 at x=0

Answer 1

y'=2x-3
plug in x = 0

Answer 2

y'=2x-3; y'(0)=2(0)-3=-3

Answer 3

Im not entirely sure how you did that.
Im supposed to find it using the formula of

(f(x+h) - x)/h

Answer 4

Oh. You haven't learned the shortcut yet. Using that, you have to expand it.
For example, look at this: http://www.analyzemath.com/calculus/Differentiation/derivative_definition.html

Answer 5

(H+x)^2 -3(x+H) - 1 -(X^2 -3X - 1)
X^2 + 2hx + H^2 - 3x - 3h - 1 - x^2 + 3x + 1

2hx + H^2 -3h / h

\[\prime= 2x\]

Its supposed to be -3, what am I doing wrong?

Answer 6

I think our teacher wants use to learn how to do it using this method before using any shortcuts.

Answer 7

y=x^2 - 3x - 1
f(x+h)= (x+h)^2 - 3(x+h) - 1
f(x)= x^2 - 3x - 1

[((x+h)^2 - 3(x+h) - 1) - (x^2 - 3x - 1)]/ h

Answer 8

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

Answer 9

I see what I did wrong,
2hx + H^2 -3h / h turns into
-3

Sorry for wasting you time, but I did learn a shortcut. Thanks!

Answer 10

No problem.