Answer:
x= -42
Step-by-step explanation:
put the liketerms together
x+35= -7
x=-35-7
note*the operation sign changes after crossing the equal sign
x= -42
(i) Given that

when
this reduces to






(ii) Differentiate
implicitly with respect to
. By the chain and product rules,

(iii) Differentiating both sides of the given equation leads to

where we use the result from (ii) for the derivative of
.
Solve for
:





From part (i), we have
and
, and substituting these leads to



as required.
3 hours is the correct answer