given function: f(x)=3x^2+6x-10

how can i find horizontal tangent of function f(x)=3x^2+6x-10 ?

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- October 8th 2009, 01:57 PMhaebinHorizontal tangent?
given function: f(x)=3x^2+6x-10

how can i find horizontal tangent of function f(x)=3x^2+6x-10 ? - October 8th 2009, 02:08 PMCalculus26
the horizontal tangent is where f ' = 0

f ' = 6x +6 = 0

at x= -1

y = f '(-1)(x+1) +f(1) = f(1)

y = -1 - October 8th 2009, 02:13 PMDeMath
- October 8th 2009, 02:19 PMhaebin
why y = -13 ?

hm... - October 8th 2009, 02:34 PMCalculus26Quote:

y = f '(-1)(x+1) +f(1) = f(1)

My mistake

should be f(-1) not f(1) - October 8th 2009, 03:27 PMhaebin
so it should be

f ' = 6x +6 = 0

at x= -1

y = f '(-1)(x+1) + f(-1)

y = f '(-1)(-1+1) + f(-1)

y = f(-1)

f(x)=3x^2+6x-10

y = 3(-1)^2 + 6(-1) - 10

= 3 - 6 - 10

= -13 ?

thank you !! :)