2. a=5/3 - 3/7
b=1/3+ 3/7
aduci la acelasi numitor: a=35/21 -9/21=26/21
b=7/21+9/21= 16/21
ma=a+b :2
26/21 + 16/21 :2 = 42/21 :2= 2:2=1
3. 27 elevi
b= 80% din f
b=?
f+ 80/100 din f= 27
f+8/10 din f=27 aduci la acelasi numitor si elimini si numitorul in acelasi timp: 10f+8f=270
18f=270
f=15
b= 80/100 din 15
b=12
4.f: |R--> |R, f(x)=2x-4
a) f(-2)+f(2)=-8
faci f(-2)= 2.(-2)-4 =-4-4=-8
f(2)= 2.2-4=4-4=0 ==> f(-2)+f(2)=-8
5.E(x)=x+1/ x^2+1 : (x-1)^2 -x(x-2)/x^2+1
x^2+1 diferit de 0 ==> x diferit de -1 ==> x apartine lui |R- {-1}
x+1/ x^2+1 : x^2-2x+1- x^2+2x/ x^2+1
x+1/ x^2+1 : 1/ x^2+1
x+1/ x^2+1 . x^2+1/1
X^2+1 se simplifica si ramane E(x)= x+1
