The Purplemath Forums

everything got divided through by "a" (step 4), which leaves the whole equation essentially unchanged. You just didn't notice, that's all. After step 5, which is not shown in your post, multiply the term "-c/a" by "4a/4a", which will give you "-4ac/4a 2 " Add ...

This is called an "arithmetic series". Each term in an arithmetic series ALWAYS has a difference of "d" between each term. Subtract any term in this sequence by the one that preceded it and the answer is always d=(I'll let you figure this one out). If you want to calculate the ac...

Expanding log₃[3SQRT(x/81)]

here are 5 BIG HINTS:

1) Product Property of Logarithms
2) A root is an exponent (find out what SQRT means!)
3) Power Property of Logarithms
4) Quotient Property of Logarithms

5) log_aa = 1

Now just do it!

...

ok, answer is (1/2)log₃x - 2

No one's gonna look at this, and I don't know if this helps, but from a Production standpoint in EconA: Skilled Labor produces y more effectively Unskilled Labor produces x more effectively EconA producing soly x or y is double the output of that of that in EconB. Graph all 3 lines on the same plane...

I guess OP isn't coming back, so the answers are

a_n= 5(3n-1)

and

S_n=(10/2)[(10)+(145)]= $775.

Those are REALLY good suggestions, the last one is actually the fastest way to solve the problem. But remember that if you ever get stuck, there is a guaranteed solution to any quadratic equation using the Quadratic Formula (and if there isn't, it means the equation is unsolvable, or at least has no...