3)
progresie aritmetică
a1=1
a2=7
________
a3=?
a4=?
________
r=a2-a1=7-1=6
a3=a2+r=7+6=13
a4=a3+r=13+6=19
4)
progresie geometrică
b1=1
q=3
__________
b5=?
b24=?
b2021=?
__________
bn = b1• q ^(n-1)
b5=b1•q⁴-¹=1•3²=9
b24=b1•q²⁴-¹=1•3²³=3²³
b2021=b1•q²⁰²¹-¹=1•3²⁰²⁰=3²⁰²⁰
5) x=✓4•9=✓36=6
6)
A=(-5;3]
b=[-2;8]
AUB = (-5;8]
A intersectat cu B (U invers ) = [-2;3]
A\B=(-5;-2)
B\A=(3;8]
