Tuesday, September 16, 2014

15^(2x-3)=3^x*5^(3x-6) x=?

We notice that we can write 15 =
3*5


We'll raise to 2x-3 both
sides:


15^(2x-3) =
3^(2x-3)*5^(2x-3)


We'll re-write the
equation:


3^(2x-3)*5^(2x-3) =
3^x*5^(3x-6)


We'll divide by 3^x and we'll
get:


3^(2x-3)*5^(2x-3)/3^x =
5^(3x-6)


We'll divide by
5^(2x-3):


3^(2x-3)/3^x =
5^(3x-6)/5^(2x-3)


We'll subtract the
exponents:


3^(2x - 3 - x) = 5^(3x - 6 - 2x +
3)


We'll combine like terms inside
brackets:


3^(x - 3) = 5^(x -
3)


We'll re-write the
equation:


3^x*3^-3 =
5^x*5^-3


3^x/3^3 =
5^x/5^3


We'll create matching bases. We'll divide by
5^x:


3^x/5^x*3^3 = 1/5^3


We'll
multiply by 3^3:


3^x/5^x =
3^3/5^3


(3/5)^x =
(3/5)^3


Since the bases are matching, we'll apply one to
one property:


x =
3


The solution of the equation is x =
3.

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