А)b1=1 q =3 n=10, bn? Sn? б) q=0,5 n=8 bn=2 b1? Sn? в) b1=2 n=7 bn=1458 q? Sn? г) q=3 bn =567 Sn=847 b1? n? помогите плиз!!  

а)b1=1 q =3 n=10, bn? Sn? [latex]\displaystyle b_n=b_1*q^{n-1}\\b_{10}=1*3^{10-1}=3^9=19683[/latex] [latex]\displaystyle S_n= \frac{b_1(q^n-1)}{q-1} [/latex] [latex]\displaystyle S_{10}= \frac{1*(3^{10}-1)}{3-1}= \frac{59049-1}{2}=29524 [/latex] б) q=0,5 n=8 bn=2 b1? Sn? [latex]\displaystyle b_8=b_1*q^7\\2=0.5^7*b_1\\b_1=2/0.5^7=2^8=256[/latex] [latex]\displaystyle S_8= \frac{b_1(q^7-1)}{q-1}= \frac{2^8(2^{-8}-1)}{0.5-1}=510 [/latex] в) b1=2 n=7 bn=1458 q? Sn? [latex]\displaystyle b_7=b_1*q^6\\1458=2*q^6\\q^6=729\\q=3[/latex] [latex]\displaystyle S_7= \frac{2(3^7-1)}{3-1}=2186 [/latex]  г) q=3 bn =567 Sn=847 b1? n?  [latex]\displaystyle S_n= \frac{b_1(3^n-1)}{2}=847\\b_n=b_1*3^{n-1}=567\\b_1= \frac{567*3}{3^n}\\S_n= \frac{ \frac{1701}{3^n}(3^n-1)}{2}=847 [/latex] [latex]\displaystyle 1701- \frac{1701}{3^n}=1694\\3^n=243\\n=5 [/latex] [latex]\displaystyle b_1=1701/3^5=7[/latex]