Question

*Пожалуйста ответьте*
a1+a4=26

a2-a5=6

a3+a5=?

Арифметическая прогрессия

Answer 1

$\displaystyle\bf\\\left \{ {{a_{1} + a_{4} =26} \atop {a_{2} - a_{5} }=6} \right. \\\\\\\left \{ {{a_{1} + a_{1} +3d=26} \atop {a_{1} +d- a_{1}-4d }=6} \right. \\\\\\\left \{ {{2a_{1} + 3d=26} \atop {-3d}=6} \right.\\\\\\\left \{ {{2a_{1} + 3d=26} \atop {d}=-2} \right.\\\\\\a_{3} +a_{5} =a_{1} +2d+a_{1} +4d=2a_{1} +6d=\\\\=2a_{1} +3d+3d=26+3\cdot(-2)=26-6=20\\\\\\Otvet \ : \ a_{3} +a_{5} =20$