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Q7
In an AP, the first term is -12 and the last term is 40. If the sum of all terms is 196, find the
common difference and number of terms.
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Respuesta :

tramserran

Answer:  d = 4, n = 14

Step-by-step explanation:

[tex]S_n=\dfrac{a_1+a_n}{2}\cdot n[/tex]

[tex]\text{Given:}\quad S_n=196, a_1=-12, a_n=40\\\\\\196=\dfrac{-12+40}{2}\cdot n\\\\392=28n\\\\14=n[/tex]

[tex]a_{n}=a_1+d(n-1)\\a_{14}=a_1+d(14-1)\\40=-12+d(14-1)\\52 = 13d\\4=d[/tex]

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