Question

Va rog am nevoie de ajutor la exercitiul aceste dau multe puncte si coroana

Answer 1

amplificam pe prima cu 3a+7 si pe a doua cu 3a-7
E(a)=(3a^2+7a-3a^2+7a-7)/9a^2-49 la puterea -1 :(3a-7)/7
E(a)=(14a-7)/9a^2-49 la puterea -1 :(3a-7)/7
E(a)=(9a^2-49)/14a-7 x 7/(3a-7)
E(a)=(3a+7)/(14a-7) x 7 
E(a)=(21a+49)/(14a-7) 
E(a)=2
(21a+49)/(14a-7)=2 
21a+49=2x(14a-7)
21a+49=28a-14
21a-28a= -14-49
-7a= -63
a= 9 

Answer 2

$E(a)= (\frac{3a ^{2}+7a-3a ^{2} +7a-7 }{9a ^{2} -49} ) ^{-1} * \frac{7}{3a-7}$
$E(a)=[ \frac{a(3a+7)-a(3a-7)-7}{9a ^{2}-49 } ] ^{-1} * \frac{7}{3a-7}$
$E(a)=( \frac{14a-7}{9a ^{2}-49 } ) ^{-1} * \frac{7}{3a-7}$
$E(a)= \frac{(3a-7)(3a+7)}{7(2a-1)} * \frac{7}{3a-7}$
$E(a)= \frac{3a+7}{2a-1}$
$\frac{3a+7}{2a-1} =2 =\ \textgreater \ 3a+7=4a-2 =\ \textgreater \ -a=-9 =\ \textgreater \ a=9$