Sunday, November 22, 2015

What are all solution of the equation 289^x-12*17^x+11=0 ?

Since 289 is a power of 17, we'll
write:


289 = 17^2


We'll raise
both sides by x;


289^x =
17^2x


We'll re-write the
equation:


17^2x - 12*17^x + 11 =
0


We'll replace 17^x by 
t:


t^2 - 12t + 11 = 0


t^2 - t
- 11t + 11 = 0


t(t - 1) - 11(t-1) =
0


(t - 1)(t - 11) = 0


We'll
cancel each factor and w'ell get:


t - 1 = 0 => t1 =
1


t - 11 = 0 => t2 =
11


17^x = t1 <=> 17^x  = 1 <=>
17^x = 17^0


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


x = 0


17^x =
t2<=> 17^x  = 11 <=> ln 17^x = ln 11 => x = ln 11/ln
17


The complete set of solutions of the
equation is {0 ; ln 11/ln 17}.

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