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anonymous
 5 years ago
y=2x is a tangent to the curve y=x^3+ax+b at x=1. Find a and b.
anonymous
 5 years ago
y=2x is a tangent to the curve y=x^3+ax+b at x=1. Find a and b.

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bahrom7893
 5 years ago
Best ResponseYou've already chosen the best response.0Tangent line is the first derivative, so: y' = 3x^2 + a; x = 1; y' = 3*1^2 + a

bahrom7893
 5 years ago
Best ResponseYou've already chosen the best response.0now slope of ur tangent line is: y= 2x; M = 2=> 3 + a = 2 => a = 1

bahrom7893
 5 years ago
Best ResponseYou've already chosen the best response.0but what the heck is b? lol im lost lemme see, kinda embarassing

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0wouldn't i just fill in a & fill in 1 for x to find b?

bahrom7893
 5 years ago
Best ResponseYou've already chosen the best response.0oh yeah, i think you do this: you need y too when x=1, so y = 2x = 2; x = 1; a = 1 2 = 1^3 + (1)*1 + b 2 = 1 1 +b => b = 2

bahrom7893
 5 years ago
Best ResponseYou've already chosen the best response.0can u check the answer?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0yes that's right thank you so much!
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