Question

Найти разность арифметической прогрессии, если a4+a6=−18, a3+a4=−3

Answer 1

$\left \{ {{ a_{4} + a_{6}=-18 } \atop { a_{3}+ a_{4} =-3 }} \right. \\\\ \left \{ {{ a_{1}+3d+ a_{1} +5d=-18 } \atop { a_{1}+2d+ a_{1} +3d=-3 }} \right.\\\\- \left \{ {{2 a_{1}+8d=-18 } \atop {2 a_{1}+5d=-3 }} \right.$
______________
3d = - 18+3
3d = - 15
d = - 5