1) Б
2) b1=8
b2=4
q=b2/b1= 1/2 =0,5 Г)
3) b4=b1×q²=2×(0,5)³=1/4 A)
4) 25; b2; 49
b2=√(25×49)=35 Б)
5) b10=b1×q⁹=2⁹=512
S10=b10×q–b1/q-1 = 512×2–1/2–1=1023 Б)
6) S=b1/1-q
b1= S(1-q)=65(1- 2/3) = 65/3 = 21 2/3.
7) b6=b1×q⁵
b9=b1×q⁸
b6/b9 = b1×q⁵/ b1×q⁸
96/768 = 1/q³
q³=768/96=8
q=2.
8) b8=b1×q⁷
384=b1×2⁷
b1=3
Sn=bn×q-b1/q-1
S8=384×2-3/2-1=765
9) b2+b3=30
b1q+b1q²=30
b1q(1+q)=30
b4-b2=90
b1q³-b1q=90
b1q(q²-1)=90
b1q(q²-1)=90
b1q(q-1)(q+1)=90
b1q(1+q)/b1q(q-1)(q+1) = 30/90
1/q-1 = 1/3
q=4.
b1q(1+q)=30
b1=30/q(1+q)= 30/20= 3/2
b5=b1×q⁴= 3/2 × 4⁴ = 384