(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Find the equation of the normal to the curve y=(6x+3)^(1/2) at the point for which x=13.

2. Relevant equations

dy/dx=dy/du*du/dx

y-y1=m(x-x1)

3. The attempt at a solution

y=(6x+3)^(1/2)

dy/dx=1/3(6x+3)^2

gradient of normal = -3(6x+3)^2

at x=13, dy/dx=-3(6x13+3)^2=19683.

obviously a silly answer and the textbook disagrees.

So at this point I could simplify y=(6x+3)^(1/2) to y=(2x+1)^2 maybe? Even after doing this, I end up with an even slightly smaller silly answer and the textbook still disagrees, unless the textbook is wrong, although this is highly unlikely.

HELP!

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# Differentiation - finding equation of normal to curve

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