Геометрич. прогрессия b1+b2=6 b1+b2+b3=7 q=? и спасибо

[latex] b_{1}+ b_{2} =6 [/latex] [latex] b_{1}+ b_{1}*q=6 [/latex] [latex] b_{1}(1+q)=6[/latex] [latex]b_{1}+ b_{2}+ b_{3}=7 [/latex] [latex]b_{1}+ b_{1}*q+ b_{1}* q^{2}=7 [/latex] [latex] b_{1}(1+q+ q^{2})=7 [/latex] [latex] \frac{1+q+ q^{2} }{1+q}= \frac{7}{6} [/latex] [latex]6+6q+6 q^{2}=7+7q [/latex] [latex]6 q^{2} -q-1=0[/latex] [latex] q_{1}=- \frac{1}{3} ; q_{2} =0.5 [/latex]