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2014-08-18T19:24:27+03:00
1) 12x + 18 +4x -12 < 9x -6 +37

16x +6 < 9x +31

16x -9x < 31 -6

5x < 25  |:5

x < 5   => x=(-α;5)

2)\frac{a-3}{a}=3 <=> a-3=3a <=> a-3a = 3 <=> -2a =3  => a= -\frac{3}{2}  \\ \frac{a-1}{a}=3 \ \ |^2  <=> \frac{(a-1)^2}{a^2}=9 <=> \frac{(a-1)(a+1)}{a^2}=9  \\ \frac{( - \frac{3}{2} -1)(a+1)}{a^2}=9 \ aducem \ la \ acelasi \ numitor\ la \ numarator \ \\ \frac{ (\frac{-3-2}{2})(a+1)}{a^2}=9 <=> \frac{ -\frac{5}{2}(a+1) }{a^2} =9  \\ \frac{a+1}{a^2}= 9 * ( -\frac{2}{5})  <=> \frac{ a+1}{a^2}= -\frac{18}{5}
La 1 ai scris bn prima oara,dar dupa
in loc de 37 ai scris 31
La 16x-9x,ti-a dat5?
37-6=31 si acolo ai dreptate, da 7x <25 => x <25/7 => x =(-infinit; 25/7)