Sunday, July 31, 2011

Solve the equation 25^(square root(x+1))+5=6*5^squareroot(x+1)

We notice that 25^sqrt(x+1) =
5^2sqrt(x+1)


We can replace 5^sqrt(x+1) by
t:


The equation will
become:


t^2 + 5 = 6t


We'll
shift all terms to the left:


t^2 - 6t + 5 =
0


We'll apply quadratic
formula:


t1 =
[6+sqrt(36-20)]/2


t1 =
(6+sqrt16)/2


t1 =(6+4)/2


t1 =
5


t2 = 1


But t1 = 5^sqrt(x+1)
=> 5 = 5^sqrt(x+1)


Since the bases are matching,
we'll apply one to one rule:
sqrt(x+1) = 1


We'll
raise to square both sides:


x + 1 = 1 => x =
0


t2 = 5^sqrt(x+1) => 1 = 5^sqrt(x+1), where 1 =
5^0


Since the bases are matching, we'll apply again one to
one rule:
sqrt(x+1) = 0


x + 1 = 0 => x =
-1


Both value are valid, therefore the
solutions of the equation are {-1 ; 0}.

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