1. ## differentials...

question : find and evaluate and compare DELTAy and dy
----------------------------------------------------------
given data:
y = x^(4)+1 x = -1 DELTAx=dx=.01

to obtain deltaY i use this equation
DELTAy = (fx+DELTAx)-f(x)
-----------------------------------------------
which when i plug in the above data i get....
DELTAy = -.99-0
DELTAy = -.99
----------------------------------------------------
the back of my book says DELTAy should be... -0.039
what am i doing wrong :/

2. Originally Posted by nuclear123
question : find and evaluate and compare DELTAy and dy
----------------------------------------------------------
given data:
y = x^(4)+1 x = -1 DELTAx=dx=.01

to obtain deltaY i use this equation
DELTAy = (fx+DELTAx)-f(x)
-----------------------------------------------
which when i plug in the above data i get....
DELTAy = -.99-0
DELTAy = -.99
----------------------------------------------------
the back of my book says DELTAy should be... -0.039
what am i doing wrong :/
$\Delta y = f(x+\Delta x)-f(x)$

$=((-.99)^4+1)-((1)^4+1)$

$dy = f'(x)\,dx$

$=4x^3\,dx$

$=4(-1)^3(.01)$