The formula for the \(n\)-th term of an arithmetic progression (A.P.) is:
\[ a_n = a + (n - 1)d \]
Where:
Given information:
Applying the formula for the 10th term with the given values:
\[ a_{10} = a + (10 - 1)d \implies -19 = 8 + 9d \]
Solving for \(d\):
\[ -19 - 8 = 9d \implies -27 = 9d \implies d = \frac{-27}{9} \implies d = -3 \]
The common difference is:
\(d = -3\)
Consider an A.P. $a_1,a_2,\ldots,a_n$; $a_1>0$. If $a_2-a_1=-\dfrac{3}{4}$, $a_n=\dfrac{1}{4}a_1$, and \[ \sum_{i=1}^{n} a_i=\frac{525}{2}, \] then $\sum_{i=1}^{17} a_i$ is equal to