two questions have solution....please check & help!

[insideout]

1)Find the derivative of y= 7^4x

My solution is:

28^4x

2) I also need help with this.... Find the derivative of y = 2x/ln2x

My solution is:

= 2x/(1/2x)
= 4x/x
= 4

 

[tkhunny]

No on both.

On the first, use this: (d/dx)a^x = a^x*ln(a)

On the second, Use the Quotient Rule. Why did you try to find the derivative of the denominator only? You must use ALL of it.

 

[insideout]

what would be the solutions to the questions....please help.

 

[insideout]

After revising my solution to the second question is:

= 2x/(1/2x)
= 4x/x
= 4 .... after this point this is what I have....

= [(ln 2x) * (2) - (2x)(1/x)] / (ln 2x)^2
= [(2ln2x - 2x/x)] / (ln 2x^2)
= [(2ln2x - 2)] / (ln 2x^2)
= [(ln2x (2-2)] / (ln 2x^2)
= (2-2) / (ln 2x)
= (1) / (ln 2x)

 

[tkhunny]

How could you possibly go from

= 2x/(1/2x)
= 4x/x
= 4 ....

to

= [(ln 2x) * (2) - (2x)(1/x)] / (ln 2x)^2
= [(2ln2x - 2x/x)] / (ln 2x^2)
= [(2ln2x - 2)] / (ln 2x^2)
= [(ln2x (2-2)] / (ln 2x^2)
= (2-2) / (ln 2x)
= (1) / (ln 2x)

Without any passage of time.

Still not quite right. The second derivative in the numerator needs work. You tell me what part that is and how to fix it.