Hello fishkeeper Originally Posted by

**fishkeeper** Im having problems with finding the first term, I will be able to do the second part of the question easily, as its just the formula.

My text book hasnt got any examples of this sort of question in it, so Im unsure how to go about trying to complete it.

thanks

With the usual notation, the sum of the first $\displaystyle 10$ terms is:

$\displaystyle 5(2a + 9d) = 50$

$\displaystyle \Rightarrow 2a+9d = 10$ ...(1)

The second term is $\displaystyle a + d$; the fifth is $\displaystyle a + 4d$. So:

$\displaystyle a+4d=3(a+d)$

$\displaystyle \Rightarrow 2a = d$

Substitute into (1):

$\displaystyle 10d=10$

$\displaystyle \Rightarrow d = 1$

$\displaystyle \Rightarrow a = \tfrac12$

OK now?

Grandad