Ответ:

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Verified answer

[tex]\displaystyle\bf\\\left \{ {{a_{4} +a_{6} =28} \atop {a_{5} +a_{11} =46}} \right. \\\\\\\left \{ {{a_{1}+3d+a_{1} +5d=28 } \atop {a_{1}+4d+a_{1} +10d=46 }} \right.\\\\\\\left \{ {{2a_{1} +8d=28} \atop {2a_{1} +14d=46}} \right. \\\\\\-\left \{ {{a_{1} +7d=23} \atop {a_{1} +4d=14}} \right. \\---------\\3d=9\\\\d=3\\\\a_{1} =14-4d=14-4\cdot 3=14-12=2\\\\Otvet: \ \boxed{a_{1} =2}[/tex]