Math help

[Xenus]

I'm doing derivates and a have the question Find an equation for the tangent line to the graph of at x = 11 of f(x)= (x-4)/(3x+5)

Using the quotient rule I get 17/(38)^2. Yet the program keeps telling me this is he wrong answer. I even put in 1444 for 38^2 because that is what it equals.

Oh and how do you find the answer to (2x+(2x+(7x)^.5)^.5)^.5 I assume it is some weird combination of the chain rule but it would be god awful long.

I get

((1/2)(-sqrt(2x+sqrt(2x+sqrt(7x)))))(2+sqrt(2x+sqrt(7x)))((1/2)(-sqrt(2x+sqrt(7x))))(2+sqrt(7x))((1/2)(-sqrt(7x)))(7)

But it says that is wrong

 

[CMAN]

I'm doing derivates and a have the question Find an equation for the tangent line to the graph of at x = 11 of f(x)= (x-4)/(3x+5)

Using the quotient rule I get 17/(38)^2. Yet the program keeps telling me this is he wrong answer. I even put in 1444 for 38^2 because that is what it equals.

Oh and how do you find the answer to (2x+(2x+(7x)^.5)^.5)^.5 I assume it is some weird combination of the chain rule but it would be god awful long.

I get

((1/2)(-sqrt(2x+sqrt(2x+sqrt(7x)))))(2+sqrt(2x+sqrt(7x)))((1/2)(-sqrt(2x+sqrt(7x))))(2+sqrt(7x))((1/2)(-sqrt(7x)))(7)

But it says that is wrong

17/(38)^2=0.011773=CORRECT, so says the TI-89 Titanium god. So the program is wrong.

 

[CMAN]

But that is only the slope, so you probably need to find the y intercept so the line y=mx+b goes through the point for the equation.

 

[Xenus]

Wouldn't that be .1724376731

And it still says no

 

[Silkworm]

Wouldn't that be .1724376731

And it still says no

No, the answer should be in the form of an equation, y=mx+b, not a numerical value because you weren't asked for only the slope or only the y-intercept.

 

[Xenus]

I meant wouldn't b= .1724376731

 

[Silkworm]

can prove it yourself by seeing if
y=mx+b == (x-4)/(3x+5)

 

[Xenus]

yes I did 7/38 = 17/(38)^2 + b I was just asking a conformastion on the number.

 

[Silkworm]

you forgot something:
7/38 = (17/38^2)*11 + b
m = 17/38^2, x = 11, y = 7/38
I got b = 79/1444 == 0.054709

 

[Xenus]

Yah I just figured that out talking to the TA through email.

Though You have any clue waht is wrong with the second question. I can't find any errors with my use of the chain rule.

Here's what I have now the TA mentioned something about taking the derivative wrong but As it is so long I have no ieda what derivative he was talking about.Then he said he was going to bed.

((1/2(2x+(2x+(7x)^.5)^.5)^-.5)(2+(2x+(7x)^.5)^.5)((1/2)(2x+(7x)^.5)^-.5)(2+(7x)^.5)((1/2)(7x)^-.5)(7))

From
sqrt(2x+sqrt(2x+sqrt(7x)))

Oh and could anyone who knows please get around to it somewhat quickly I only have 1 hour and 20 minutes left. And no I am not demanding that you tell me it.

Bastard I win it equals (2+(2+7/(2*sqrt(7*x)))/(2*sqrt(2*x+sqrt(7*x))))/(2*sqrt(2*x+sqrt(2*x+sqrt(7*x)))) now to fifure out how it gets there. Yay for derivative calculators.