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Which term of the AP : 121, 117 , 113,....., is its first term negative term? |
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Answer» Given AP is:121, 117, 113, ................First term a = 121Common difference d = 117-121 = -4Let nth term is the first negative term in APNow nth tern in AP = a + (n-1)*d= 121 + (n - 1)*(-4)= 121 - 4n + 4= 125 - 4nNow, we have to find the suitable value of n so that the value of (125 - 4n) is negative.⇒ 125 - 4n < 0⇒ 125 < 4n⇒ 4n > 125⇒ n > 125/4=> n > 31.25Since the term can not be in decimal form (term is always taken a positive integer)\xa0So, n = 32\xa0Now, by taking value of n = 32, we getnth term = 125 - 4× 32 = 125 - 128 = -3This is the first negative term in the series.So, n = 32Hence, the\xa032nd\xa0term is the first negative term in AP. 32nd term...... |
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