Question

I think THIS is the chain rule

Let y = u**(9/2) and u = 8 x + 1.

what is the derivitive?

Answer 1

** means ^

Answer 2

dy/dx = dy/du * du/dx

Answer 3

yes

Answer 4

i mean dy/dx=8

Answer 5

dy/du = (9/2) u ^ (7/2)
now plug in u = 8x + 1 and multiply by 8
du/dx = 8

Answer 6

dy/du=9/2x^1-9/2

Answer 7

wait do i use the chain rule?

Answer 8

64x+8

Answer 9

i think 9/2u^7/2 is wrong

Answer 10

if y = u^(9/2)
dy/du = (9/2 ) u^ (9/2 - 1 )

this is the power rule: if y=ax^n dy/du = anx^(n-1)

Answer 11

i did that but i think 9/2u^7/2 is wrong

Answer 12

you do use chain rule
dy/dx = dy/du * du/dx

Answer 13

yes

Answer 14

i thought you do the power rule inside the chain rule since its in brackets

Answer 15

ok y = u^(9/2) and u = 8x + 1 right?

Answer 16

correct

Answer 17

dy/dx = (9/2) u ^ (7/2) * 8
= (9/2) (8x + 1)^(7/2) * 8 ( plugging in u = 8x+1)
= 36 ( 8x + 1)^(7/2)

Answer 18

theres something wrong w/ dy/du

Answer 19

thats the only problem because du/dx is right

Answer 20

so the process is f=right but one number is wrong

Answer 21

lets look at y = x^n them dy/dx = n x ^ (n-1)
now let u = x and n = 9/2
then y = u^(9/2)
so dy/du = (9/2) u ^(9/2 - 1)
= (9/2) u^ (7/2) because 9/2 - 1 = 9/2 - 2/2 = 7/2