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La suma de los primeros $\\var{n1}$ términos de una progresión aritmética es $\\var {s1}$ y el término de lugar $\\var {n2}$ de la misma serie es $\\var {T}$.
", "advice": "Recuerde que la fórmula para la suma de los primeros n términos de una progresión aritmética es \\(S_n=\\frac{n}{2}(2a+(n-1)d)\\).
\nLa suma de los \\(\\var{n1}\\) primeros términos de una progresión aritmética es \\(\\var{s1}\\)
\n\\(\\frac{\\var{n1}}{2}(2a+\\simplify{{n1}-1}d)=\\var{s1}\\) ecuación (i)
\nLa fórmula para el enésimo término de una progresión aritmética es \\(T_n=a+(n-1)d\\).
\nEl término de lugar \\(\\var{n2}\\) de la misma serie es \\(\\var{T}\\)
\n\\(a+\\simplify{{n2}-1}d=\\var{T}\\) ecuación (ii)
\nTenemos dos ecuaciones simultáneas. Podemos eliminar el término \\(a\\) .
\n\\(\\var{n1}a+\\simplify{({n1}-1)*{n1}/2}d=\\var{s1}\\) ecuación (i)
\n\\(\\var{n1}a+\\simplify{{n1}*({n2}-1)}d=\\simplify{{n1}*{T}}\\) ecuación (ii)*\\(\\var{n1}\\)
\n\\(\\simplify{({n1}-1)*{n1}/2-{n1}*({n2}-1)}d=\\simplify{{s1}-{n1}*{T}}\\)
\n\\(d=\\frac{\\simplify{{s1}-{n1}*{T}}}{\\simplify{({n1}-1)*{n1}/2-{n1}*({n2}-1)}}\\)
\n\\(d=\\simplify{({s1}-{n1}*{T})/(({n1}-1)*{n1}/2-{n1}*({n2}-1))}\\)
\nUsando este resultado y sustituyendo en la ecuación (ii) podemos encontrar el valor de \\(a\\)
\n\\(a+\\simplify{({n2}-1)*({s1}-{n1}*{T})/(({n1}-1)*{n1}/2-{n1}*({n2}-1))}=\\var{T}\\)
\n\\(a=\\var{T}-\\simplify{({n2}-1)*({s1}-{n1}*{T})/(({n1}-1)*{n1}/2-{n1}*({n2}-1))}\\)
\n\\(a=\\simplify{{{T}-({n2}-1)*({s1}-{n1}*{T})/(({n1}-1)*{n1}/2-{n1}*({n2}-1))}}\\)
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\nCalcular el valor del primer término de la progresión. \\(a\\) = [[1]]
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