find the point where the normal line to y = x + root x at (4,6) crosses the y-axis.

Question

phi · Answer

did you find the equation for the slope of the curve?

anonymous · Answer

wait.. i'll solve for the slope

anonymous · Answer

take the derivative
replace $x$ by $4$ 
that gives you the slope
take the negative reciprocal, that give you the slope of the normal line
use the point slope formula with the point $(4,6)$ to find the equation of the normal line $y=mx+b$

then $b$ is where it crosses the y axis

anonymous · Answer

the value of b is the answer then?

anonymous · Answer

yes, that is the y intecept

anonymous · Answer

ok.. thanks.. i'll try solving for it

phi · Answer

Here is a plot of the scenario

anonymous · Answer

thanks!
what i got was 31/5 .. is this correct?

phi · Answer

how ?

anonymous · Answer

i follow the steps satelite gave

phi · Answer

I think you wandered off the path...

anonymous · Answer

why??

phi · Answer

see the plot I posted up above

anonymous · Answer

where is the normal line there?

phi · Answer

the red line

anonymous · Answer

so what do you think is wrong with my answer? is the steps given by satelite somehow have mistakes? i just followed it

phi · Answer

what did you get for the slope ?

phi · Answer

first, what did you get for the derivative?

anonymous · Answer

owh wait.. i got a mistake

anonymous · Answer

b = 46/5 .. i believe that is the correct answer now?

phi · Answer

yes,  9.2  which matches the plot

anonymous · Answer

9.3 :)) thanks so much! help me again.. i'll post a question :)

phi · Answer

9.3 ?

anonymous · Answer

yes.. divide 46 by 5 right ? then it will be 9... remainder is 15.. that will be 3.. so 9.3?

phi · Answer

5*9= 45

anonymous · Answer

lol.. i got a mistake again. sorry.. yes.. 9.2