Question

ma poate ajuta la sub 2, 1 c?

Answer 1

$A=1/2*| \left|\begin{array}{ccc}2^{n}&3^{n}&1\\2^{n+1}&3^{n+1}&1\\2^{n+2}&3^{n+2}&1\end{array}\right||=1/2*| \left|\begin{array}{ccc}2^{n}&3^{n}&1\\2^{n}*2&3^{n}*3&1\\2^{n}*4&3^{n}*9&1\end{array}\right||=$
$1/2*|2^{n}*3^{n}* \left|\begin{array}{ccc}1&1&1\\2&3&1\\4&9&1\end{array}\right|| =1/2*|6^{n}*(3+18+4-12-9-2)|=$
$=1/2*|6^{n}*2|$
Dar aria este 216, deci avem:
[tex]1/2*|6^{n}*2|=216 =\ \textgreater \ |6^n*2|=432 [/tex]
Caz 1:
$6^{n}*2=432 =\ \textgreater \ 6^n=216 =\ \textgreater \ n=3$
Caz 2:
$6^{n}*2=-432 =\ \textgreater \ 6^n=-216$
Ecuatia nu are solutii, deoarece un numar pozitiv ridicat la orice putere nu are ca rezultat un numar negativ.
n=3