Question

Rezolvati in N ecuatiile:
a) x²-x=72
b) $2^{x-1}*3^{x}=432$
c) $2^{x-5}+2^{x-1}-2^{x-3}-2^{x-2}+2^{x-1}+2^{x}=156$
Rezolvati in N inecuatia:
d) 81:(x-9)>9 si x:5$\geq$2

Answer 1

a) x²-x=72 <=> x(x+1)=72 __8•9=72 => x=8.________________________________b) 2^{x-1}*3^{x}=432 <=> 2^{x}*2*3^{x}=432 <=> 2^{x}*3^{x}=432:2 <=> (2*3)^{x}=216 <=> 6^{x}=216 .Stim ca:6^{3}=216 => x=3.___________________________ ____d.)81:(x-9)>9 <=> 81>9•(x-9) <=> 81:9>x-9 <=> 9>x-9 <=> 9+9>x <=> 18>x. Si x:5≥2 <=> x≥2•5 <=> x≥10