derive formula for sum of first n natural numbers
nick9:
by 1,2,3,4,5&5,4,3,2,1
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S= 1, 2, 3..., n
it is an AP with a=1 and d=1
S= n/2 (2a+(n-1) d)
=n/2 (2+(n-1))
=n/2 (n+1)
it is an AP with a=1 and d=1
S= n/2 (2a+(n-1) d)
=n/2 (2+(n-1))
=n/2 (n+1)
plz by 1,2,3,4,5&5,4,3,2,1
means how do u want ans
s5=1+2+3+4+5 also s5=5+4+3+2+1 ana than s10 and s30
this is derivation of ur ques n if u want to find s5 den u jus hv to put the value of A n D ull ht it also d second thing u rote 5+4+,...... is not sum of first natural nos coz it reverse but if apply d values of even dis in formula ull get ams
Which term of 24,23×1÷4,22×1÷2,21×3÷4 is first negative term
as such no negative term but I think its 2nd one . m nt sure,, n sry if m wrong
n did u get ans of ur first que
yes
nd 2nd ques is of AP
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