Product Rule

**jgv115** · June 6th 2010, 12:17 AM

I'm new to all this stuff so bear with me...

I'm given $y =2x(8x+6)$

I need to find $y'$

So i do it...

$\frac {dx}{dy} = u\frac{dv}{dx} + v\frac {du}{dx}$

$2x.\frac{d(8x+6)}{dx} + (8x+6).\frac {d2x}{dx}$

$16x+12 + 16x +12$

$32x +24$

But when I check on my calculator it says $32x+12$

**Prove It** · June 6th 2010, 12:30 AM

Originally Posted by jgv115

I'm new to all this stuff so bear with me...

I'm given $y =2x(8x+6)$

I need to find $y'$

So i do it...

$\frac {dx}{dy} = u\frac{dv}{dx} + v\frac {du}{dx}$

$2x.\frac{d(8x+6)}{dx} + (8x+6).\frac {d2x}{dx}$

$16x+12 + 16x +12$

$32x +24$

But when I check on my calculator it says $32x+12$

$y = 2x(8x+6)$ .

$\frac{dy}{dx} = u\,\frac{dv}{dx} + v\,\frac{du}{dx}$

$= 2x(8) + (8x + 6)(2)$

$= 16x + 16x + 12$

$= 32x + 12$ .

**jgv115** · June 6th 2010, 12:40 AM

Hey that's exactly what my book says! But I always get different.

$= 2x(8) + (8x + 6)(2)$

I don't understand how you get $2x(8)$

How can $\frac{d(8x+6)}{dx}$ become 8?

**Prove It** · June 6th 2010, 12:57 AM

Originally Posted by jgv115

Hey that's exactly what my book says! But I always get different.

$= 2x(8) + (8x + 6)(2)$

I don't understand how you get $2x(8)$

How can $\frac{d(8x+6)}{dx}$ become 8?

The derivative of $8x$ is $8$ and the derivative of $6$ is $0$ .

So the derivative of $8x + 6$ is $8 + 0 = 8$ .

**jgv115** · June 6th 2010, 01:04 AM

oohh!!!!!!!! Thanks so much!!!!!!!

If I have $\frac {d(7x+6)}{dx}$

Then would it be $7$ ??

**Prove It** · June 6th 2010, 02:37 AM

Originally Posted by jgv115

oohh!!!!!!!! Thanks so much!!!!!!!

If I have $\frac {d(7x+6)}{dx}$

Then would it be $7$ ??

Correct.

**jgv115** · June 7th 2010, 02:47 AM

Thanks Prove It!! I appreciate the help!

Thread: Product Rule

LinkBack

Thread Tools

Display

Product Rule

Similar Math Help Forum Discussions

[SOLVED] quick question on product rule and equality rule for logs

Finding dy/dx of equation using both chain rule and product rule

Derivatives - product rule + chain rule

Help with a question involving chain rule + product rule (derivative)

Intergration help, reverse chain rule, product rule

Search Tags