deret: (1+2)+(2+3)+(3+4)+(4+5)+.....+(24+25)=

deret2 tersebu dapat ditulis 3 + 5+ 7+ 9 +...+ 49
mencari n nya terlebih dahulu

Un = a + (n - 1)×b
49 = 3 + (n - 1)×2
46 = 2n - 2
48 = 2n
n = 24
maka
[tex]sn = \frac{n}{2} (2a + (n - 1) \times b) \\ s24 = \frac{24}{2} (2(3) + (24 - 1) \times 2) \\ s24 = 12(6 + 23(2)) \\ s24 = 12(6 + 46) \\ s24 = 12(52) \\ s24 = 624[/tex]