Question

Sum of series : 1+2+3+ …………………… + n is


()

(+1)

2


() ( + 1)

()

(+1)(+2)

2


() none of these.​

Answer 1

Answer:

$\huge{\mathfrak{\red{Answer}}}$

${\Large{series = 1 + 2 + 3 + 4...... \\ the \: given \: seris \: is \: in \: ap \\ \\ here \\ first \: term(a) = 1 \\ common \: difference(d) = 2 - 1 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 1 \\ we \: know \: that \\ t(n) = a + (n - 1)d \\ \: \: \: \: \: \: \: \: \: = 1 + (n - 1)1 \\ \: \: \: \: \: \: \: \: \: = 1 + n - 1 \\ \: \: \: \: \: \: \: \: \: = n}}$

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