Find the derivative of f(x) = 8×2 + 11x at x = 7.?

Question

The answer choices are 123, -147, 156, and 189. I have gotten to this point: 8h+8x-11.Now what?

Dr. Juanita Wolff · Accepted Answer

In order to find the derivative of f(x) = 8x² + 11x at x = 7, you need to first differentiate f(x) = 8x² + 11x, and after you’re done you’ll plug in 7, i.e. making use of Liebniz Notation: f(x) = x^n → f'(x) = nx^(n – 1) to differentiate f(x) = 8x² + 11x, then f'(x) = 2*8x^(2 – 1) + 1*11x^(1 – 1) f'(x) = 16x + 11, where x = 7, then by substitution you’ll have f'(x) = 16(7) + 11 f'(x) = 112 + 11 f'(x) = 123 …Ans.

Dr. Juanita Wolff · Answer

f(x) = 8x^2 + 11xf ‘(x) = 16x + 11 [@ x = 7]f ‘(x) = 123euclidI have gotten to this point: 8h+8x-11.Now what?Additional DetailsSo I see that you got an answer but how’d you get the 16x?the real question is: how did you get (8h + 8x – 11) ??lim [f(x + h) – f(x)]/hh->0{[8(x + h)^2 + 11(x + h)] – [8x^2 + 11x]}/h= {[8(x^2 + 2xh + h^2) + 11x + 11h] – (8x^2 + 11x)}/h =(8x^2 + 16xh + 8h^2 + 11x + 11h – 8x^2 – 11x)/h =(16xh + 8h^2 + 11h)/hlim [h(16x + 8h + 11)/h] = 16x + 11x->0that is where 16x + 11 comes from…show your work !

Dr. Juanita Wolff · Answer

That’s not right.the result should be f ‘ ( x ) = 16x + 11 f ‘ ( 7 ) = 16( 7 ) + 11 f ‘ ( 7 ) = 123

Dr. Katlynn Swaniawski II

Find the derivative of f(x) = 8×2 + 11x at x = 7.?

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