Question

how many terms of an ap 21

Answer 1

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Answer 2

$hi \: mate \: \\ \\ sum \: of \: n \: terms \: of \: ap \: is \: given \: by \: this \: formul \\ \\ sn \: = n \div 2(2a + (n - 1)d) \\ \\ where \: a \: is \: ist \: term \: n \: is \: number \: of \: terms \: and \: d \: is \: common \: difference \\ \\ sn \: = 0 \: \: \: \: given \\ \\ 0 = n \div 2(2 \times 21 + (n - 1)3) \\ \\ n \: = 15$

So, number of terms must be added is 15