Second derivative question (2 Viewers)

[sprytex]

Find f''(1) if f(t) = t(2t - 1)^7

Can anyone help with this?

Answer: f''(1) = 196.

Thanks

 

[kman16]

f'(t) = 14t(2t - 1)^6 + (2t - 1)^7 (Using the Product Rule)

f"(t) = 14t x 12(2t - 1)^5 +14(2t - 1)^6 + 14(2t - 1)^6
= 168t(2t - 1)^5 + 28(2t - 1)^6

Therefore: f"(1) = 168(1) + 28(1)
= 196

 

[McLovinFanboy]

f'(t) = 4t(2t - 1) + (2t - 1)^2 (Using the Product Rule)

= 8t^2 - 4t + (2t - 1)^2

f"(t) = 16t - 4 + 4(2t - 1)
= 24t - 8

Therefore: f"(1) = 24(1) - 8
= 16

Your solution is wrong, f"(1) = 16

Got the same

 

[sprytex]

f'(t) = 4t(2t - 1) + (2t - 1)^2 (Using the Product Rule)

= 8t^2 - 4t + (2t - 1)^2

f"(t) = 16t - 4 + 4(2t - 1)
= 24t - 8

Therefore: f"(1) = 24(1) - 8
= 16

Your solution is wrong, f"(1) = 16

f''(1) = 196 was in the back of the textbook..

edit: wow i meant ^7, not ^2. sorry

 

[McLovinFanboy]

Please don't tell me it is Maths In Focus.

If so, burn it.

 

[sprytex]

Please don't tell me it is Maths In Focus.

If so, burn it.

Yeah, it is lol.

Also, I get f''(1) = 184, not 196 like the textbook says. (with the ^7, not ^2)

 

[bobmcbob365]

 

[sprytex]

View attachment 26839

Thank you

 

[kman16]

I edited my original solution

 

[sprytex]

I edited my original solution

Thank you. I see what I was doing wrong now...haha.