# Understanding derivitaves

1. Apr 4, 2008

### Mol_Bolom

I think I finally figured out derivitaves, but not sure...

The derivative/differential of x in
x is 1
3x + 5 is 3
5x^2 - 2 is 10

And breaking down a quadratic thus

3x^5 + 2x^3 + 5x - 1
The first derivative is 15x^4 + 6x^2
The second derivative is 60x^3 + 12x
Third 180x^2
Fourth 360x
And final 360.

2. Apr 4, 2008

### Werg22

No, first and third are wrong.

1. 15x^4 + 6x^2 + 5
2. 60x^3 + 12x
3. 180x^2 + 12
4. 360x
5. 360

3. Apr 4, 2008

### uman

The derivative of $$5x^2-2$$ is actually $$10x$$.

4. Apr 4, 2008

### Mol_Bolom

Ah...That was the area I had a problem with...The final solitary number...

5. Apr 4, 2008

### HallsofIvy

Staff Emeritus
The derivative (not differential) of 5x2- 2 at at x= 1 is 10. More generally, the derivative of 5x2- 2 at any x is 10x. The differential of x is dx, the differential fo 3x+ 5 is 3dx and the differential of 5x2- 2 is 10x dx.

The first derivative is 15x4+ 6x2+ 5

Well, I wouldn't call it "final". That's the fourth derivative. The fifth derivative, and all succeeding derivatives is 0.

6. Apr 4, 2008

### ice109

don't you mean the differential of y?

isn't the differential of x : dx?

7. Apr 5, 2008

### sutupidmath

I don't see any
y's in there. It can be any variable expressed as a function of x.
I think this is what Halls said also!

8. Apr 5, 2008

woops