BrainIess
BrainIess BrainIess
  • 06-07-2017
  • Mathematics
contestada

Solve 2(25^x) = 3 - 5^x

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ghanami
ghanami ghanami
  • 06-07-2017
hello : 
25 = 5²
25^x = ( 5² ) ^x = (5^x)²
let : 5^x = t .....  t > 0
the equation : 
 2(25^x) = 3 - 5^x equiv :
2t² =3 -t    and : 
 5^x = t .....  t > 0
2t² +t -3 =0
the discriminant : Δ = b² -4ac = (1)² -4(2)(-3) = 25 = 5²
t1 = (-1-5)/4  ( refused  :  t > 0 )
t2 = (-1+5)/4 =1
but:  5^x = t 
 5^x = 1
the solution is : x=0

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