combinari n∈ n si n>3
3· n! / 3! ( n-3) ! - 4n +7 =0
( n -1 ) · n /2 -4n + 7=0 n² - 9n +14 =0
n = 2 fals ; n=7
2 . conditie x +2 > 0 ⇒ x > -2
x³ -2x +4 >0 ⇒ ( x+2) · ( x² -2x +2 ) >0 daca x> - 2
x∈ ( -2 , +∞)
rez. ec. x³ -2x +4 = x² +4x +4 ⇒ x³- x² -6x =0
x ( x -3) ·( x+2 )=0 x = 0 ; x=3 ; x=-2 fals
3 . f'(x) = e^x · ( x-1 +1 ) = x· e^x II Ox daca panta este =0
f'(x) =0 daca x =0
ec.tg y - f( 0) = f'(0)
y +1 =0
y =-1
