We use the following formula , rules and
notations::
d/dxf(x) = f'(x) or
(f(x))'
d/dx (kx^n) =
k*nx^(n-1).
d/dx{ f(x)*g(x) } = f'(x)g(x) -
f(x)g('x).
d/dx{ f(x)/g(x)} = [f'(x)*g(x)-
f(x)*g'(x)}/(g(x))^2.
d/dx f(g(x)) = (df/dg )g'(x) , also
called chain rule
d/dx ln f(x) = {1/f(x)
}f'(x)
..............
Given
f(x) = ln[(sqrt(x+4)*(x+3)^2)/(sqrt3(x+5)) + 50?
RHS : 50
is treated as the 2nd term. And sqrt3(x+3) is treated as
(sqrt3)(x+5).
LHS : the one sided rectangular bracket [ is
ignored as there is no right pair inthe expression.
WE
consider:
f(x) = u(x)/v(x)
+50,
where u(x) =
ln(sqrt(x+4)*(x+3)^2).
Therefore f'(x) = {u(x)/v(x)}'
+(50)'
f'(x) = {u'(x)v(x)-u(x)v,(x)}/{v(x)}^2
..............(1), as (50)' = 0.
u'(x) =
1/sqrt(x+4)*(x+3)^2 * {sqrt(x+4)*(x+3)^2}'
u'(x) =
{(1/2)(x+4)^(-1/2)*(x+3)^2 +
(x+4)^(1/2)*2(x+3)}/sqrt(x+4)*(x+3)^2
u'(x)={(x+3)^2
+4(x+4)(x+3)}/2(x+4)(x+3)^2
u'(x) = {x^2+6x+9+4x^2+28x+48}/
2(x+4)(x+3)62
u'(x) =
(5x^2+34x+57)/2(x+4)(x+3)^2
u'(x) =
(5x+19)(x+3)/2(x+4)(x+3) ^2
u'(x)
=(5x+19)/2(x+4)...........(2)
v(x) =
(sqrt3)(x+5)
v'(x) =
(sqrt3)(x+5)'
v'(x) =
sqrt3.
Substituting in (1) , the values
obtained in (2) and (3), we get:
f'(x) =
{{(5x+19)/2(x+4)}*(sqrt3)(x+5) + ln(sqrt(x+4)*(x+3)^2) *(sqrt3)(x+5)}/
((sqrt3)(x+5))^2
f'(x) = {sqrt3(5x+19)(x+5)
+2(sqrt3)(x+4)ln(sqrt(x+4)*(x+3)^2)}/3(x+5)^2.
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