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anonymous
 5 years ago
The function y=x^4+bx^2+8x+1 has a horizontal tangent and a point of inflection for the same value of x. What must be the value of b?
anonymous
 5 years ago
The function y=x^4+bx^2+8x+1 has a horizontal tangent and a point of inflection for the same value of x. What must be the value of b?

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anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0so f ' (x) = 0 and f ' ' (x) = 0 for the same x . so f '(x) = f '' (x) f ' = 4x^3 + 2bx + 8 = f '' (x) = 12x^2 + 2b

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0but that still doesn't give me the value of b... do i set it equal to 0?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0you have to solve that equation

myininaya
 5 years ago
Best ResponseYou've already chosen the best response.1we have two equations 4x^3+2bx+8=0 and 12x^2+2b=0 I solve the bottom one for b and replace the b in the first equation with 6x^2

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.04x^3 + 2bx + 8= 12x^2 + 2b

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0oh thats smarter myininya has it

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0my way involves a bit of work

myininaya
 5 years ago
Best ResponseYou've already chosen the best response.1if you do this correctly you should get x=1 so now we can find b since b=6x^2 then b=6(1)^2=6

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0got it thank you!! :)

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0i'm going to keep posting questions so feel free to answer :) lol... i have my ap test on wednesday so i'm reviewing a lot

myininaya
 5 years ago
Best ResponseYou've already chosen the best response.1and you could have done it cantorset's way but it is a bit more thinking down his path

myininaya
 5 years ago
Best ResponseYou've already chosen the best response.1i will show you if you want. i will do it on paper and scan it and post it

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0I'll try working on it in a bit, but I like the way you taught me better, seems a lot easier.

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0wow.. looks like a lot of work :)
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