Question

найдите два первых членов геометрической прогрессии BN который б3=36, б7= 2 1/4​

Answer 1

$\left \{ {{b_{7}=2\frac{1}{4}} \atop {b_{3}=36 }} \right.\\\\:\left \{ {{b_{1}*q^{6}=2,25} \atop {b_{1}* q^{2}=36 }} \right.\\-------\\q^{4} =0,0625\\\\q_{1,2}=\pm \sqrt[4]{0,0625}=\pm0,5\\\\1)q_{1} =-0,5\\\\b_{1}=36:(-0,5)^{2} =36:0,25=144\\\\b_{2}=b_{1}*q_{1} =144*(-0,5)=-72\\\\2)q_{2} =0,5\\\\b_{1}=36:0,5^{2} =36:0,25=144\\\\b_{2}=b_{1}*q_{2} =144*0,5=72\\\\Otvet:\boxed{1)b_{1}=144;b_{2}=-72 , \ 2)b_{1} =144;b_{2}=72}$