Math, asked by devaresuhani, 1 year ago

3) How many terms of the AP 16,14, 12. are needed to give the sum 60

answers
explain why do we do get two​

Answers

Answered by karanjotgaidu
3

ANSWER :

n = 5 or n = 12 is the answer

EXPLANATION :

a = 16, d = - 2, Sn = 60

Sn = n/2 (2a + (n-1)d)

60 = n/2 (2×16 + (n-1)-2)

120 = n(32 - 2n +2)

120 = 34n - 2n²

2n² - 34n + 120 = 0

n² - 17n + 60 = 0.......... (1)

n² - 12n - 5n +60 = 0

n(n-12) - 5(n-12) = 0

n-5 = 0 or n-12 = 0

n = 5 or n = 12

We get two answers because equation (1) is a quadratic equation so it will have 2 roots

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