(x^(1/2)+x^(-1/2))^7
T4=T(3+1)=
Comb de 7 luate cate 3*(x^(1/2))^4 *(x^(-1/2))³=
comb de 7 luatecate 3* x²*x^(-3/2)= Comb de 7 luatecate 3 *x^(1/2)=
=(7!/(3!*4!) )* √x=
=(5*6*7)/6*√x=35√x
5. a.b=3*1-2*4=3-8=-5
6.presupunem ca BC are ecuatia y=-x-1 sau, implicit, x+y+1=0
intr-adevar B si C verifica ecuatia ; cum prin 2 puncte distincte trece o drepat si numai una, inseamna ca aceasta este ecuatia
distanta de la A (1;2) la BC=|1*1+1*2+1|/√(1²+2²)=4/√5=(4√5)/5
