Question

progresie geometrica​

Answer 1

Răspuns:

Explicație pas cu pas:

u3=u2×q=u1×q²

u6=100=u5×q=u4×q²=u3×q³=4/5×q³=100    ⇒q³/5=5²     q=∛125=5

u1×q²=4/5         u1×5²=4/5      u1=2/5√5=2√5/25

n=3

Sn=n(u1+u3)/2    S3=3(2√5/25+4/5)/2=6(√5+10)/25·2=3(√5+10)/25

u3n-1=u1×5^3n=2×5^(1/2)×5^3n=2×5^(3n+1/2)