Question

Deduce the formula Sn n/2 (a+l)?​

Answer 1

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

This is the answer

Hope it helps you mate

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Answer 2

Answer:

same proof, just say that L = a + (n-1)d

Sn = 0.5n(2a + (n-1)d)

Sn = 0.5n(a + a + (n-1)d)

Sn = 0.5n(a + L)