# In an arithmetic series, if S7=56, and d=5, then how do you find A1?

Feb 9, 2016

${a}_{1} = 26$

#### Explanation:

We know that in an AP, ${n}^{t h}$ term is given by
a_n= a_1 + (n – 1)d
where ${a}_{1}$ is the first term and $d$ is common difference.

Given ${a}_{7} = 56 \mathmr{and} d = 5$, substituting in the general expression and solving for ${a}_{1}$
56= a_1 + (7 – 1)5
${a}_{1} = 26$