Question

find the horizontal tangeant of y=4x^2+16x+21

Answer 1

could you find dy/dx ?

Answer 2

I figured it out!! :D is it x= -2?

Answer 3

thats the x-coordinate of the horizonatal tangent
the equation of horizontal tangent will be of the form y= constant
so, from x=2 and your original equation, y=...
you just need to find the y co-ordinate

Answer 4

could you help me on y=x^4-2x^2+1 instead? (:

Answer 5

so just plug it in? :)

Answer 6

yes,
for the 1st problem
just put x=-2 in your equation y=4x^2+16x+21

Answer 7

for y=x^4-2x^2+1
what did u get dy/dx as ?

Answer 8

4x^3-4x

Answer 9

@hartnn

Answer 10

did u get y=5 as your final answer for 1st ?

yes, thats correct
4x^3-4x =0
solve this for x

Answer 11

using quadratic?

Answer 12

or how? lol

Answer 13

factor out the 'x' first
4x (x^2-1) = 0

x=0 , or x^2-1 =0

Answer 14

oohhh! is it x=0, x=1, x=-1 ?

Answer 15

sorry for late replies
yes, those are correct
find y value from that

Answer 16

okay, thanks(: