Need help with actual change and approx change in calc!?

Question

Let f be the function defined by y = f(x)= 5 x^2.
Find the actual change in y when x changes from 1 to 1.2.
_________?


Also, Use the differential dy of the function f to find the APPROXIMATE change in y when x changes from 1 to 1.2
__________?

Answer 1

f(1.2)==5*1,44=7,20
f(1)=5

delta f =7,20-5=1,80


dy=10x
change=10*1,2-10*1
=12-10=2