Arithmetic progression - find the first term and the common

[nae99]

the sum of the firts 8 term of an AP is 56, and the 6th term is 4 times the sum of the 2nd the 3rd. find the first term and the common difference.

[Jonasmathwork]

s_8 = 56

s= n/2[2a + (n-1)d]
56 = 4[2a + 7d]

2a + 7d = 14

T_6 = 4 (T_2 + T_3)
a + 5d = 4(a + d + a + 2d)
a + 5d = 8a +12d
7a + 7d = 0
a + d = 0

2a + 7d = 14
2a + 2d = 0
_ _
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5d = 14

d = 14/ 5

a + d = 0
a = - 14/5

In my schooling i have more problems with Arithmetic Progression but thanks to all math sites to help me a lot.